# HTML Reference Manual

Last Modified: 8 September 1995

## Index

Introduction
Conformance
Sandia Requirements
General Syntax
Comments
`A`, `ABBREV`, `ACRONYM`, `ADDRESS`, `AU`, `B`, `BANNER`, `BASE`, `BASEFONT`, `BIG`, `BLINK`, `BLOCKQUOTE`, `BODY`, `BQ`, `BR`, `CAPTION`, `CENTER`, `CITE`, `CODE`, `CREDIT`, `DD`, `DEL`, `DFN`, `DIR`, `DIV`, `DL`, `DT`, `EM`, `FN`, `FIG`, `FONT`, `FORM`, `H1`, `H2`, `H3`, `H4`, `H5`, `H6`, `HEAD`, `HP`, `HR`, `HTML`, `I`, `IMG`, `INPUT`, `INS`, `ISINDEX`, `KBD`, `LANG`, `LH`, `LI`, `LINK`, `LISTING`, `MENU`, `META`, `NEXTID`, `NOBR`, `NOTE`, `OL`, `OPTION`, `OVERLAY`, `P`, `PERSON`, `PLAINTEXT`, `PRE`, `Q`, `S`, `SAMP`, `SELECT`, `SMALL`, `STRIKE`, `STRONG`, `SUB`, `SUP`, `TAB`, `TABLE`, `TD`, `TEXTAREA`, `TH`, `TITLE`, `TR`, `TT`, `U`, `UL`, `VAR`, `WBR`, `XMP`
Uniform Resource Locator (URL)
Special Characters
Standard Icons
Disclaimer
Acknowledgements

## Introduction

HTML is an evolving language which is used to construct documents which can be viewed by World Wide Web browsers. HTML is attempting to be standardized by the WWW consortium but that standard is also evolving. HTML is currently defined at Version 2, but the final version of the RFC has not yet been officially published. This Reference Manual will be updated to the official RFC whenever that is published. The Version 2 Specification also declared some earlier elements obsolete. There is active work on-going to finalize the specifications of a Version 3 of HTML which contains significant new features. HTML+ was a draft of the proposals for Version 3. In addition, there is some talk of an interim Version 2.1 to standardize a few of the more desired Version 3 features earlier than the expected final agreement on a Version 3.

This document attempts to include most of the extensions in the current proposal for Version 3, since some Version 3 features are beginning to be implemented in some browsers at use at Sandia. (ed:Most "Elements Allowed Within..." and "Allowed In Content Of..." still need updating, as does the meanings of some new Version 3 attributes.) While this may introduce confusion by describing non-existent features, there is value in being aware of the proposed directions in this language. The inclusion of Version 3 proposals intentionally excludes the additions to handle Mathematical Expressions since this area is still in progress. For further information about Version 3, see Acknowledgements.

Not all browsers implement all features of Version 2. In addition, some browsers define and handle their own extensions. A browser is supposed to ignore any element or attribute of the language that it is not designed to handle.

## Conformance

As of the IETF HTML BOF of 26 July 1994, the Version 2 Standard Specification defined five levels of conformance of the HTML Language elements. Browsers can choose (and declare) what level of conformance they fulfill.

Level 0
  Mandatory. Heading, lists, anchors, etc.
  (A text only browser is expected to have Level 0 conformance.)
Level 1
  Images, Emphasis
Level 2
  Forms, Character Definitions
Level 3
  Tables, Figures, etc.
  (proposed in Version 3)
Level 4
  Mathematical formulae
  (proposed in Version 3, not existing practice, not yet included in this reference)

## Sandia Requirements

The Integrated Information Services Division of Sandia National Laboratories has established a set of requirements for HTML documents prepared at Sandia National Laboratores. These requirements are an attempt to maintain document consistency, provide some configuration management hooks, automatically insert links between documents and identify document ownership within Sandia's Internal Web. For individuals with access to Sandia's Internal Web, a more complete specification of those requirements is available. In addition to requirements, that specification also references documents with style guide suggestions for Sandia HTML authors. While this Reference Manual attempts to identify the Sandia requirements, for any conflicts, the specification page on the Internal Web takes precedence.

In addition to the SGML identification line described in General Syntax, and the HTML elements and attributes which are required (see `ADDRESS`, `BODY`, `HEAD`, `HTML`, `IMG`, `META`, `LINK`, `TITLE`), all documents shall have a "point-of-contact" name identified in the document as part of the `ADDRESS` element that is e-mail enabled by surrounding the name with the `<A>` element. Sandia authors should use Sandia's cgi-bin e-mail program to generate a mail message submission form by setting the HREF attribute of the A element to one of the addresses identified in the Sandia specification document. Until all the browsers which the CIO organization of Sandia suppports, and for which Sandia has a site license, accept the newly emerging `mailto:` URL access code, Sandia authors of documents on our Internal web are discouraged from setting the HREF attribute of the A element to `"mailto:ename@sandia.gov"` This mechanism is acceptable for documents on the external web, but authors should also display the e-mail address of the "point-of-contact" name so that manually initiated e-mail is possible.

All Sandia documents shall also display a line indicating the date the document was last modified. This is usually placed with the ADDRESS element at either the beginning or end of the document. Recommended format is: `Last Modified: 18 Apr 1995`

Any Sandia document which is part of a set of HTML subdocuments which form a sequence or hierarchy should include two specific LINK elements identifying the REL values of `next` and `previous`. In addition, the author should also place icons or text enabled with the <A> element at the beginning and/or end of the BODY section to make it easy to jump to the document next or previous in the sequence. Only one `next` and one `previous` relationship may be specified in a document.

## General Syntax

HTML is an application of ISO Standard 8879:1986 -- Standard Generalized Markup Language (SGML). SGML is a system for defining structured document types, and markup languages to represent instances of those document types. HTML is one such markup language. Its syntax follows the syntax of SGML. An HTML file is an ASCII file of text which also includes instructions to a browser, mostly about displaying the text. To formally identify the file as containing HTML elements, the beginning of the file should contain a line in SGML syntax identifying the version of HTML being used. For HTML Version 2.0, this line is
`<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">`

Sandia Requirements
  The SGML specification line identifying the file as HTML is required before the `<HTML>` element in the file. It should either specify the version number of HTML to which the file conforms by using a line like the one above, or simply specify that the file is HTML by using the line:
  `<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">`

Unless explicitly instructed otherwise, the browser normally treats all white space that is not a blank (e.g. tabs, end-of-line characters, etc.) as a single blank, and collapses multiple white space to a single blank. The browser instructions consist of HTML elements which are HTML element names, optionally followed by HTML attributes, all surrounded by "<" and ">" Attributes may be followed by an equals sign and some "value". White space is allowed around the equals sign. The standard requires that the "value" must be surrounded by single or double quotes, but many browsers do not enforce this syntax. The maximum length of "value" (after parsing) is defined as 1024 characters. Most HTML elements are designed to surround some content, usually text, and thus have both a beginning and ending tag. The ending tag is simply the element name preceded by a "/" all surrounded by "<" and ">" HTML names must begin with a letter and are followed by up to 33 letters, digits, periods, or hyphens. The standard defines the HTML names in upper case, but (except for Special Characters) browsers are supposed to ignore the case of HTML names.

## Comments

Description
  To include comments in an HTML document that will be ignored by the HTML browser, surround them with `<!--` and `-->`. After the beginning comment delimiter, all text up to the next occurrence of `-->` is ignored. Hence comments cannot be nested. White space is allowed between the closing `--` and `>`, but not between the opening `<!` and `--`.
Minimum Attributes
  `<!--characters... -->`
Common Usage
  `<!--
  characters...
  characters...
  -->`
Variations
  Not all browsers will properly handle HTML elements (i.e. an "`<`") inside of a comment. Some browsers will treat as comments any element that begins with "`<!`" and not require the two dashes at the beginning "`<!--`" or the end "`-->`" of the commented text. This syntax is actually SGML, and the browser is simply ignoring unrecognized SGML commands. Such browsers will terminate this "comment" upon the first occurance of a "`>`". Some browsers prohibit the double dash "`--`" sequence from appearing anywhere within the commented text except at the end. Version 2 specifies the double dash at beginning and end as required. A few early browsers recognized an element `<comment>` `</comment>`. The Version 2 specification delcares this element obsolete. Version 2 is proposing to add the SGML comment syntax to HTML elements. This proposal would begin a comment with a double dash encountered inside any HTML element (but not inside quotes), and treat everything as comments (including any "`>`", "`<`", or quote character) until the next occuring double dash. Such syntax would allow HTML elements within a comment.

## A

Description
  The A element brackets (or anchors) a piece of text (and/or image) which is identified as a hypertext link. The A element must have either an HREF attribute or a NAME attribute. The HREF attribute identifies a destination URL, and the bracketed text is rendered as a hypertext link to the URL. Browsers will display the contents of an A element with an HREF attribute in a special manner to indicate that if the contents are selected, the browser will execute that hypertext link. The NAME attribute identifies a destination tag, and the bracketed text is thereby identified as an available hypertext target within this document. Browsers do not display the contents of an A element with a NAME attribute in any special way. However, an A element with an HREF attribute can now be constructed by using the document URL suffixed with `#name`. This will load the document, but will position the display starting at the location of this NAME tag. An A element with an HREF attribute can also be constructed to jump directly to this destination tag within the same document by a URL consisting solely of `#name` The presence of `REL=`relation in document A with HREF to document/object B identifies a relationship that B has to A that A recognizes/authorizes/verifies. The presence of `REV=`relation of the identical relation in document B with HREF to document/object A identifies a desired/expected/claimed relationship that B has to A, but must be verified by checking with A.
Minimum Attributes
  `<A HREF="..." >characters... </A>`
  or
  `<A NAME="..." >characters... </A>`
All Possible Attributes
  `<A HREF="..." NAME="..." REL="..." REV="..." URN="..." TITLE="..." METHODS="..." ID="..." LANG="..." CLASS="..." MD="..." SHAPE="...">characters... </A>`
Elements Allowed Within...
  `<IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  HTML+ and Version 3 propose changing the NAME attribute to ID and adding an ID attribute for various elements including the paragraph and heading elements. Version 3 specifically identifies NAME as obsolete and replaced by ID. At present REV and REL are rarely used or supported, and are Level 1 attributes, but are of growing interest to automated document environments. These relationships are more commonly identified in the HEAD of the document using the LINK element. REL and REV are a comma-separated set of relationship(s) of the HREF link. These relationships and their semantics are registered with the HTML authority. Examples are `UseIndex, UseGlossary, Annotation, Reply, Embed, Precedes, Subdocument, Present, Search, Supersedes, History, Made, Owns, Approves, Supports, Refutes, Includes, Interested.` URN is for a Universal Resource Number, and is not currently used or supported, and is a Level 1 attribute. TITLE is little used or supported, and is a Level 1 attribute, but is expected to be the title of the HREF document. METHODS is little used or supported, but is expected to be a comma-separated list of HTTP METHODS supported by the object and accessible to the user. LANG, CLASS, and MD are the general attributes proposed by Version 3. SHAPE is proposed by Version 3 to provide a mechanism to define multiple A elements and corresponding "hotzones" within the proposed FIG element, to perform the equivalent function of ISMAP without the need for writing a responding cgi-bin program. A is a Level 0 element.

## ABBREV

Description
  The ABBREV element changes the character rendering of the contents of the element to logically represent abbreviations.
Minimum Attributes
  `<ABBREV>characters... </ABBREV>`
All Possible Attributes
  `<ABBREV ID="..." LANG="..." CLASS="...">characters... </ABBREV>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The ABBREV element is a Version 3 proposed element. All character definition elements are Level 2.

## ACRONYM

Description
  The ACRONYM element changes the character rendering of the contents of the element to logically represent acronyms.
Minimum Attributes
  `<ACRONYM>characters... </ACRONYM>`
All Possible Attributes
  `<ACRONYM ID="..." LANG="..." CLASS="...">characters... </ACRONYM>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The ACRONYM element is a Version 3 proposed element. All character definition elements are Level 2.

## AU

Description
  The AU element changes the character rendering of the contents of the element to logically represent the name of an author.
Minimum Attributes
  `<AU>characters... </AU>`
All Possible Attributes
  `<AU ID="..." LANG="..." CLASS="...">characters... </AU>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The AU element is a Version 3 proposed element. All character definition elements are Level 2.

## ADDRESS

Description
  The ADDRESS element defines a separated multi-line set of text to be rendered for address information.
Minimum Attributes
  `<ADDRESS>characters... </ADDRESS>`
All Possible Attributes
  `<ADDRESS ID="..." LANG="..." CLASS="..." CLEAR=left|right|all|"..." NOWRAP>characters... </ADDRESS>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I> <P>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <FORM>`
Variations
  ADDRESS text is typically rendered in italics. The ID, LANG, CLASS, CLEAR, and NOWRAP attributes are proposed in Version 3. ADDRESS is a Level 0 element.
Sandia Requirements
  An ADDRESS element is required to identify a "point-of-contact". For details, see the Sandia Requirements.

## B

Description
  The B element changes the physical rendering of the contents of the element to a bold font.
Minimum Attributes
  `<B>characters... </B>`
All Possible Attributes
  `<B ID="..." LANG="..." CLASS="...">characters... </B>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  Browsers who do not have bold may render in some other manner. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## BANNER

Description
  The BANNER element is proposed for corporate logos, navigation aids, disclaimers and other information which shouldn't be scrolled with the rest of the document.
Minimum Attributes
  `<BANNER>characters... </BANNER>`
All Possible Attributes
  `<BANNER ID="..." LANG="..." CLASS="...">characters... </BANNER>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `<BODY>`
Variations
  This is a proposed Version 3 element.

## BASE

Description
  The BASE element provides the URL base to be used for any relative URL links in this document. It must be a complete file name, and is usually the original URL of this document. If this file is moved, having the BASE set to the original URL eliminates the need to also move all the documents which are identified by relative URL links in this document.
Minimum Attributes
  `<BASE HREF="...">`
All Possible Attributes
  `<BASE HREF="...">`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<HEAD>`
Variations
  This is a Level 0 element.

## BASEFONT

Description
  Change the document base font size to one of the seven defined sizes. The default is 3.
Minimum Attributes
  `<BASEFONT SIZE=1|2|3|4|5|6|7>`
All Possible Attributes
  `<BASEFONT SIZE=1|2|3|4|5|6|7>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The BASEFONT element is a Netscape extension.

## BIG

Description
  The BIG element changes the physical rendering of the contents of the element to a bigger font than normal text, if practical.
Minimum Attributes
  `<BIG>characters... </BIG>`
All Possible Attributes
  `<BIG ID="..." LANG="..." CLASS="...">characters... </BIG>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The BIG element is proposed in Version 3. All character definition elements are Level 2.

## BLINK

Description
  The BLINK element changes the physical rendering of the contents of the element to a blinking font.
Minimum Attributes
  `<BLINK>characters... </BLINK>`
All Possible Attributes
  `<BLINK>characters... </BLINK>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  This element is not listed in the standard, and many browsers ignore this element. Many users find the use of this element annoying. It should be restricted to short term use for new information. Netscape 1.1N permits users to disable the rendering of this element.

## BLOCKQUOTE

Description
  The BLOCKQUOTE element defines a separated multi-line set of text to be rendered as quoted text.
Minimum Attributes
  `<BLOCKQUOTE> </BLOCKQUOTE>`
All Possible Attributes
  `<BLOCKQUOTE> </BLOCKQUOTE>`
Elements Allowed Within...
  `<H1> <H2> <H3> <H4> <H5> <H6> <P> <UL> <OL> <DIR> <MENU> <DL> <PRE> <BLOCKQUOTE> <FORM> <ISINDEX> <HR> <ADDRESS>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <FORM> <LI>`
Variations
  The contents of the BLOCKQUOTE element is typically rendered slightly indented both left and right, and/or italic font. Early browsers displayed the contents with a vertical line of ">" characters down the left margin to indicate quotation in the Internet mail style. Version 3 proposes replacing the BLOCKQUOTE element with the BQ element. BLOCKQUOTE is a Level 0 element.

## BODY

Description
  The BODY element contains all the content of the document, as opposed to the HEAD, which contains information about the document. All displayable elements should be within the content of the BODY.
Minimum Attributes
  ``
All Possible Attributes
  `<BODY ID="..." LANG="..." CLASS="..." BACKGROUND="..." BGCOLOR="#rrggbb" TEXT="#rrggbb" LINK="#rrggbb" VLINK="#rrggbb" ALINK="#rrggbb"> </BODY>`
Elements Allowed Within...
  `<H1> <H2> <H3> <H4> <H5> <H6> <P> <UL> <OL> <DIR> <MENU> <DL> <PRE> <BLOCKQUOTE> <FORM> <ISINDEX> <HR> <ADDRESS>`
Allowed In Content Of...
  `<HTML>`
Variations
  The HTML, HEAD, and BODY elements were introduced with Version 2, and are currently optional, but are considered Level 0 elements by the Version 2 standard. Version 3 proposes the attributes ID, LANG, CLASS, and BACKGROUND. Netscape 1.1 includes the BACKGROUND attribute, which is a URL to point to an image to be reproduced to fill the background of the document. The BGCOLOR, LINK, VLINK, and ALINK attributes are Netscape 1.1 extensions.
Sandia Requirements
  The HTML, HEAD and BODY elements are required.

## BQ

Description
  The BQ element defines a multi-line set of text to be rendered as quoted text. The content of the BQ element may optionally contain the CREDIT element.
Minimum Attributes
  `<BQ> </BQ>`
All Possible Attributes
  `<BQ ID="..." LANG="..." CLASS="..." CLEAR=left|right|all|"..." NOWRAP> </BQ>`
Elements Allowed Within...
  `<CREDIT>
  -others TBD-`
Allowed In Content Of...
  `<BQ>
  -others TBD-`
Variations
  The BQ element is proposed in Version 3 as a replacement for the BLOCKQUOTE element. Version 3 does not indicate the typical rendering of the contents of the BQ element, but does indicate that it may not imply text separation.

## BR

Description
  The BR element breaks for a new line, but does not produce separation of text.
Minimum Attributes
  `<BR>`
All Possible Attributes
  `<BR CLEAR=left|right|all|"..." ID="..." LANG="..." CLASS="...">`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  The CLEAR attribute is a Netscape extension and was added to force the line break to clear possible floating graphic images. Version 3 includes CLEAR, and proposes the remaining attributes. The BR element is Level 0.

## CAPTION

Description
  The CAPTION element is used to label a table or figure.
Minimum Attributes
  `<CAPTION>characters... </CAPTION>`
All Possible Attributes
  `<CAPTION ALIGN=top|bottom|left|right ID="..." LANG="..." CLASS="...">characters... </CAPTION>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `<FIG> <TABLE>`
Variations
  The CAPTION element is proposed in Version 3. There is some discussion that the only values that make sense for the ALIGN attribute when CAPTION is used in the contents of the TABLE element are `top|bottom` This element is an extension in Netscape 1.1.

## CENTER

Description
  All contents within the CENTER element is to be centered between the current left and right margin.
Minimum Attributes
  `<CENTER>characters... </CENTER>`
All Possible Attributes
  `<CENTER>characters... </CENTER>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `<A> -TBD-`
Variations
  The CENTER element is a Netscape extension. It was provided as an alternative to the HTML+ and Version 3 `ALIGN="center"` proposed new attribute for all the text block elements such as the `<P>` paragraph and `<H?>` header elements. There is still debate as to which mechanism is preferred, but the current Version 3 specification only includes the ALIGN attribute, not the CENTER element.

## CITE

Description
  The CITE element changes the character rendering of the contents of the element to logically represent a citation.
Minimum Attributes
  `<CITE>characters... </CITE>`
All Possible Attributes
  `<CITE ID="..." LANG="..." CLASS="...">characters... </CITE>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  This is typically rendered in italics. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## CODE

Description
  The CODE element changes the character rendering of the contents of the element to logically represent computer code.
Minimum Attributes
  `<CODE>characters... </CODE>`
All Possible Attributes
  `<CODE ID="..." LANG="..." CLASS="...">characters... </CODE>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  This is usually rendered in a fixed-width font. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## CREDIT

Description
  The CREDIT element is used to name the source of a block quotation or figure.
Minimum Attributes
  `<CREDIT>characters... </CREDIT>`
All Possible Attributes
  `<CREDIT ID="..." LANG="..." CLASS="...">characters... </CREDIT>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `<BQ> <FIG>`
Variations
  The CREDIT element is proposed in Version 3. Version 3 does not indicate the typical rendering for the contents of the CREDIT element, nor whether that rendering should be different or separated from the enclosing block quotation or figure.

## DD

Description
  The DD element identifies the separated multi-line definition item in a DL definition list.
Minimum Attributes
  `<DD>characters...`
All Possible Attributes
  `<DD>characters... </DD>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I> <P> <UL> <OL> <DIR> <MENU> <DL> <PRE> <BLOCKQUOTE> <FORM> <ISINDEX>`
Allowed In Content Of...
  `<DL>`
Variations
  This is typically rendered as normal text, indented. Most browsers assume that the contents of the element ends when it encounters a `<DT>` or another `<DD>` or the `</DL>` element to end the list, and thus do not require the ending tag. All list elements are Level 0.

## DEL

Description
  The DEL element changes the character rendering of the contents of the element to logically represent deleted text, for instance in modifications in legal documents.
Minimum Attributes
  `<DEL>characters... </DEL>`
All Possible Attributes
  `<DEL ID="..." LANG="..." CLASS="...">characters... </DEL>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The DEL element is a Version 3 proposed element. While this will typically be rendered by strikethru characters, the DEL element is preferred over using the S or STRIKE elements. All character definition elements are Level 2.

## DFN

Description
  The DFN element changes the character rendering of the contents of the element to logically represent a defining instance of a term.
Minimum Attributes
  `<DFN>characters... </DFN>`
All Possible Attributes
  `<DFN ID="..." LANG="..." CLASS="...">characters... </DFN>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The DFN element is not widely implemented, but is usually rendered bold or bold italic. The ID, LANG, and CLASS attributes are proposed in Version 3. It is a Version 2 and Version 3 proposed element.

## DIR

Description
  The DIR element defines an unordered list consisting of a number of single-line `<LI>` elements, usually less than 20 characters in length. These may be arranged in columns across the page.
Minimum Attributes
  `<DIR></DIR>`
All Possible Attributes
  `<DIR COMPACT> </DIR>`
Elements Allowed Within...
  `<LI>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <FORM> <LI>`
Variations
  This list type is not commonly implemented, and is often rendered identically to UL. Specifying `<UL PLAIN WRAP=HORIZ>` is proposed in Version 3 as a replacement for the DIR element. All list elements are Level 0.

## DIV

Description
  The DIV element is proposed to be used with the CLASS attribute to represent different kinds of containers, e.g. chapter, section, abstract, or appendix.
Minimum Attributes
  `<DIV>characters... </DIV>`
All Possible Attributes
  `<DIV ID="..." LANG="..." CLASS="..." ALIGN=left|center|right|justify NOWRAP CLEAR=left|right|all|"...">characters... </DIV>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `<BODY>`
Variations
  This is a proposed Version 3 element. `<DIV ALIGN=center>` is the proposed replacement for the non-standard `CENTER` element.

## DL

Description
  The DL element defines a definition list. Each item in the list is expected to have two parts, identified by the `<DT>` and `<DD>` elements.
Minimum Attributes
  `<DL></DL>`
All Possible Attributes
  `<DL COMPACT ID="..." LANG="..." CLASS="..." CLEAR=left|right|all|"..."> </DL>`
Elements Allowed Within...
  `<LH> <DT> <DD>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <FORM> <LI>`
Variations
  The COMPACT attribute suggests rendering the list in a physically compact way, but is not implemented by many browsers. Version 3 proposes the general ID, LANG, CLASS, and CLEAR attributes. To obtain a specific look, it has been the practice to construct a DL with DD elements but empty or missing DT elements. Version 3 proposes a new NOTE element as the preferred alternative to achieve the effect desired. All list elements are Level 0.

## DT

Description
  The DT element identifies the separated term item in a DL definition list.
Minimum Attributes
  `<DT>characters...`
All Possible Attributes
  `<DT>characters... </DT>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<DL>`
Variations
  This is typically rendered in a bold font, but not indented. Most browsers assume that the contents of the element ends when it encounters a `<DD>` or another `<DT>` or the `</DL>` element to end the list, and thus do not require the ending tag. All list elements are Level 0.

## EM

Description
  The EM element changes the character rendering of the contents of the element to logically emphasize the text.
Minimum Attributes
  `<EM>characters... </EM>`
All Possible Attributes
  `<EM ID="..." LANG="..." CLASS="...">characters... </EM>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  Usually rendered in italics. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## FIG

Description
  The FIG element is an advanced form of the IMG element to define an image, with optional overlays, text elements and "hotzones", to be inserted within a document. The structure of the contents of the FIG element expects a series of optional overlay images defined by OVERLAY elements, followed by an optional CAPTION element, followed by text to be presented as an alternative to the image(s) and which may contain normal text elements as well as hypertext links defined by A elements with SHAPE attributes to identify "hotzones" on the image, finally completed by an optional CREDIT element.
Minimum Attributes
  `<FIG SRC="..."></FIG>`
All Possible Attributes
  `<FIG SRC="..." ID="..." LANG="..." CLASS="..." CLEAR=left|right|all|"..." NOFLOW MD="..." ALIGN=left|right|center|justify|bleedleft|bleedright WIDTH=value HEIGHT=value UNITS="..." IMAGEMAP="..."></FIG>`
Elements Allowed Within...
  `<OVERLAY> <CAPTION> <CREDIT>
  -TBD-` (ed: all normal markup elements?)
Allowed In Content Of...
  `-TBD-`
Variations
  The FIG element is proposed in Version 3 as a sophisticated alternative to the IMG element, especially to enhance the capabilities of the ALT text for non-graphical presentations of HTML documents, as well as a way to accomplish the common use of the ISMAP attribute of the IMG element without the need for a responding cgi-bin program.

## FN

Description
  The FN element logically identifies text to be presented as a footnote. The reference location for the footnote is expected to be an A element whose HREF attribute references the ID of the FN element.
Minimum Attributes
  `<FN ID="...">characters... </FN>`
All Possible Attributes
  `<FN ID="..." LANG="..." CLASS="...">characters... </FN>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The FN element is a Version 3 proposed element. Version 3 specifies that when practical, the browser should render the FN element as pop-up notes. Version 3 does not specify an expected rendering when the footnote text is simply displayed where it occurs in the document. However, Version 3 does state that the FN element does not imply text separation. Therefore, common practice expects that the contents of the FN element would begin with a markup element which produces separation, e.g. the P element.

## FONT

Description
  The FONT element changes the font size of the following characters to one of the seven defined sizes, or plus or minus from the document BASEFONT size.
Minimum Attributes
  `<FONT SIZE=[+|-]1|2|3|4|5|6|7>`
All Possible Attributes
  `<FONT SIZE=[+|-]1|2|3|4|5|6|7>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The FONT element is a Netscape extension.

## FORM

Description
  The FORM element creates a fill-out form. The browser permits the user to enter information in the fields of the form and sends this information to a cgi-bin script on a server identified as a URL by the ACTION attribute. METHOD=GET (the default) appends the input information to the ACTION URL which becomes the value of the environment variable `QUERY_STRING`. METHOD=POST (the preferred) sends the input information in a data body which is available on `stdin` with the data length set in the environment variable `CONTENT_LENGTH`. Form data is a stream of `name=value` pairs separated by the `&` character. Each name=value pair is URL encoded, i.e. spaces are changed into the plus character and some characters are encoded into hexadecimal. At least one of the following is expected inside the FORM contents: INPUT, SELECT, TEXTAREA.
Minimum Attributes
  `<FORM></FORM>`
All Possible Attributes
  `<FORM ACTION="..." METHOD=GET|POST ENCTYPE="..." SCRIPT="..."> </FORM>`
Elements Allowed Within...
  `<H1> <H2> <H3> <H4> <H5> <H6> <P> <UL> <OL> <DIR> <MENU> <DL> <PRE> <BLOCKQUOTE> <ISINDEX> <HR> <ADDRESS> <INPUT> <SELECT> <TEXTAREA>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <LI>`
Variations
  Only the default value of `application/x-www-form-urlencoded` is currently defined for the ENCTYPE attribute, but is expected to allow all registered MIME types. Version 2 only defines ACTION for the `http:` access type. Version 3 proposes the SCRIPT attribute to specify a URL which contains a limited syntax script to be downloaded to the browser for execution to preprocess the FORM output before sending it to the ACTION destination. All elements concerning FORM are Level 2.

## H1

Description
  The H1 element identifies text to be separated and displayed as the most prominent header.
Minimum Attributes
  `<H1>characters... </H1>`
All Possible Attributes
  `<H1 ID="name" LANG="..." CLASS="..." ALIGN=left|center|right|justify CLEAR=left|right|all|"..." SEQNUM=nnn SKIP=nnn DINGBAT=entity-name SRC="..." MD="..." NOWRAP>characters... </H1>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <FORM>`
Variations
  The specification recommends that a document use the header elements in order, without breaks, beginning with H1. (ed: I have not identified a browser that enforces this.) The ID attribute is proposed in HTML+ and Version 3 to replace the NAME attribute in the A element to establish internal hyperlink destinations. All other attributes are proposed in Version 3. Typical rendering is bold, very large font, centered; when printed causes a page break. Headings are Level 0 elements.

## H2

Description
  The H2 element identifies text to be separated and displayed less prominently than H1 but more prominently than H3.
Minimum Attributes
  `<H2>characters... </H2>`
All Possible Attributes
  `<H2 ID="name" LANG="..." CLASS="..." ALIGN=left|center|right|justify CLEAR=left|right|all|"..." SEQNUM=nnn SKIP=nnn DINGBAT=entity-name SRC="..." MD="..." NOWRAP>characters... </H2>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <FORM>`
Variations
  The specification recommends that a document use the header elements in order, without breaks, beginning with H1. (ed: I have not identified a browser that enforces this.) The ID attribute is proposed in HTML+ and Version 3 to replace the NAME attribute in the A element to establish internal hyperlink destinations. All other attributes are proposed in Version 3. Typical rendering is bold, large font, flush left. Headings are Level 0 elements.

## H3

Description
  The H3 element identifies text to be separated and displayed less prominently than H2 but more prominently than H4.
Minimum Attributes
  `<H3>characters... </H3>`
All Possible Attributes
  `<H3 ID="name" LANG="..." CLASS="..." ALIGN=left|center|right|justify CLEAR=left|right|all|"..." SEQNUM=nnn SKIP=nnn DINGBAT=entity-name SRC="..." MD="..." NOWRAP>characters... </H3>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <FORM>`
Variations
  The specification recommends that a document use the header elements in order, without breaks, beginning with H1. (ed: I have not identified a browser that enforces this.) The ID attribute is proposed in HTML+ and Version 3 to replace the NAME attribute in the A element to establish internal hyperlink destinations. All other attributes are proposed in Version 3. Typical rendering is italic, large font, slightly indented. Headings are Level 0 elements.

## H4

Description
  The H4 element identifies text to be separated and displayed less prominently than H3 but more prominently than H5.
Minimum Attributes
  `<H4 LANG="..." CLASS="..." ALIGN=left|center|right|justify CLEAR=left|right|all|"..." SEQNUM=nnn SKIP=nnn DINGBAT=entity-name SRC="..." MD="..." NOWRAP>characters... </H4>`
All Possible Attributes
  `<H4 ID="name">characters... </H4>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <FORM>`
Variations
  The specification recommends that a document use the header elements in order, without breaks, beginning with H1. (ed: I have not identified a browser that enforces this.) The ID attribute is proposed in HTML+ and Version 3 to replace the NAME attribute in the A element to establish internal hyperlink destinations. All other attributes are proposed in Version 3. Typical rendering is bold, normal font, indented. Headings are Level 0 elements.

## H5

Description
  The H5 element identifies text to be separated and displayed less prominently than H4 but more prominently than H6.
Minimum Attributes
  `<H5>characters... </H5>`
All Possible Attributes
  `<H5 ID="name" LANG="..." CLASS="..." ALIGN=left|center|right|justify CLEAR=left|right|all|"..." SEQNUM=nnn SKIP=nnn DINGBAT=entity-name SRC="..." MD="..." NOWRAP>characters... </H5>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <FORM>`
Variations
  The specification recommends that a document use the header elements in order, without breaks, beginning with H1. (ed: I have not identified a browser that enforces this.) The ID attribute is proposed in HTML+ and Version 3 to replace the NAME attribute in the A element to establish internal hyperlink destinations. All other attributes are proposed in Version 3. By default, Netscape uses a font size for H5 that is smaller than default text. For most other browsers, the font size for all headers is at least as large as the default text. Typical rendering is italic, normal font, indented. Headings are Level 0 elements.

## H6

Description
  The H6 element identifies text to be separated and displayed less prominently than H5 but more prominently than default text.
Minimum Attributes
  `<H6>characters... </H6>`
All Possible Attributes
  `<H6 ID="name" LANG="..." CLASS="..." ALIGN=left|center|right|justify CLEAR=left|right|all|"..." SEQNUM=nnn SKIP=nnn DINGBAT=entity-name SRC="..." MD="..." NOWRAP>characters... </H6>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <FORM>`
Variations
  The specification recommends that a document use the header elements in order, without breaks, beginning with H1. (ed: I have not identified a browser that enforces this.) The ID attribute is proposed in HTML+ and Version 3 to replace the NAME attribute in the A element to establish internal hyperlink destinations. All other attributes are proposed in Version 3. By default, Netscape uses a font size for H6 that is smaller than default text. For most other browsers, the font size for all headers is at least as large as the default text. Typical rendering is bold, normal font, not indented. Headings are Level 0 elements.

## HEAD

Description
  The HEAD contains general information about the document. None of the elements authorized to exist in the contents of the HEAD are displayed; the displayed material is found within the BODY.
Minimum Attributes
  ``
All Possible Attributes
  `<HEAD> </HEAD>`
Elements Allowed Within...
  `<TITLE> <ISINDEX> <BASE> <META> <NEXTID> <LINK>`
Allowed In Content Of...
  `<HTML>`
Variations
  The HTML, HEAD, and BODY elements were introduced with Version 2, and are currently optional, but are considered Level 0 elements by the Version 2 standard. Version 3 also proposes the new elements of RANGE and STYLE as allowed within a HEAD.
Sandia Requirements
  The HTML, HEAD and BODY elements are required.

## HPn

Description
  The HP set of elements, with n=1,2,... provided a mechanism to highlight the characters in a phrase with one of a set of browser defined highlight mechanisms.
Minimum Attributes
  `<HPn>characters... </HPn>`
All Possible Attributes
  `<HPn>characters... </HPn>`
Elements Allowed Within...
Allowed In Content Of...
Variations
  The Version 2 specification has declared these elements as obsolete.

## HR

Description
  The HR element produces a separated horizontal dividing line drawn completely across the screen.
Minimum Attributes
  `<HR>`
All Possible Attributes
  `<HR ID="..." CLASS="..." CLEAR=left|right|all|"..." SRC="..." MD="..." SIZE=number WIDTH=number|percent ALIGN=left|right|center NOSHADE>`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <FORM> <PRE>`
Variations
  The ID, CLASS, CLEAR, SRC, and MD attributes are proposed in Version 3. SRC is proposed to specify a custom image for the rule. Some browsers draw the line only within the current text margins (which may be indented on left and/or right due to lists, etc.) SIZE, WIDTH, ALIGN, and NOSHADE attributes are Netscape extensions. The HR element is Level 0.

## HTML

Description
  The HTML element is intended to bracket the entire HTML text in the document. All other HTML elements are inside the start and end of the HTML element.
Minimum Attributes
  ``
All Possible Attributes
  `<HTML> </HTML>`
Elements Allowed Within...
  `<HEAD> <BODY>`
Allowed In Content Of...
  ``
Variations
  The HTML, HEAD, and BODY elements were introduced with Version 2, and are currently optional, but are considered Level 0 elements by the Version 2 standard.
Sandia Requirements
  The HTML, HEAD and BODY elements are required.

## I

Description
  The I element changes the physical rendering of the contents of the element to an italics (or slanted) font.
Minimum Attributes
  `<I>characters... </I>`
All Possible Attributes
  `<I ID="..." LANG="..." CLASS="...">characters... </I>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## IMG

Description
  The IMG element allows an image file to be inserted within an HTML document along with the text. The ALT attribute defines text that will be displayed if the image is not or cannot be displayed by the browser. The ALT text can contain special characters, but it cannot contain markup. The SRC attribute identifies a URL for retrieving the image. The ISMAP attribute is only meaningful if the IMG element is within the contents of an A element, and a responding cgi-bin program has been established at the URL identified by the HREF attribute of the A element. If a single A element spans both an image and text, the cgi-bin program will receive the HREF input values, if any, if the text is selected, or the x,y cursor coordinates if the image is selected. For references to this advanced feature, see Acknowledgements.
Minimum Attributes
  `<IMG SRC="...">`
All Possible Attributes
  `<IMG SRC="..." ALT="..." ISMAP ID="..." LANG="..." CLASS="..." MD="..." ALIGN=bottom|middle|top|left|right|texttop|absmiddle|baseline|absbottom HEIGHT=value WIDTH=value UNITS="..." BORDER=value LOWSRC="..." HSPACE=value VSPACE=value>`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <SAMP> <STRONG> <TT> <VAR>`
Variations
  The attributes BORDER, HEIGHT, WIDTH, HSPACE, VSPACE, and LOWSRC are Netscape extensions. Version 3 proposes adding the WIDTH and HEIGHT attributes. Version 1 defines only `bottom|middle|top` as values for the ALIGN attribute. The additional values for the ALIGN attribute are Netscape extensions, and include the capability to define floating images. Version 3 proposes adding only the (`LEFT|RIGHT`) values for ALIGN to identify images that imply that text can float around the image. Some image capable browsers will display the ALT text until the full image is retrieved. The Version 2 specification states that Level 0 conformance must accept the element, but Level 1 conformance is required before it displays the image. Version 3 proposes the generalized attributes ID, LANG, CLASS, and MD. In addition, it adds the UNITS attribute for use by the WIDTH and HEIGHT attributes to define units other than pixels. Version 3 proposes a FIG element as an advanced alternative to the IMG element, for more sophisticated multi-part overlay images, more control over text that is the equivalent of ALT, and with the proposed SHAPE attribute on the A element a method to perform the common use of the ISMAP attribute without the need for a responding cgi-bin program.
Sandia Requirements
  The ALT attribute and a value describing the image is required. If known, the BORDER, HEIGHT, and WIDTH attributes are recommended as they improve download performance on some browsers. If used, the HEIGHT and WIDTH attributes shall specify the actual size of the stored image in pixels.

## INPUT

Description
  The INPUT element is used to specify a simple input field as part of the contents in a FORM element. `TYPE=text` is default. `NAME` defines the symbolic name of the field returned to the server on submission and must be present for all but `TYPE=submit|reset`. For `TYPE=checkbox|radio`, multiple INPUT elements may have the same NAME value. `VALUE` is used to specify a default. For `TYPE=text|password` VALUE defines default text to be returned, which normally is null. For `TYPE=checkbox|radio` VALUE defines the value returned when the checkbox or radio is selected, which normally is "on". For `TYPE=submit|reset` VALUE defines the label for the pushbutton. `CHECKED` defaults the checkbox or radio to selected. `SIZE` and `MAXLENGTH` are only used with `TYPE=text|password`. `SIZE` is the physical size of the displayed input field expressed in characters or characters,rows. `MAXLENGTH` is the maximum number of characters that are accepted as input.
Minimum Attributes
  `<INPUT>`
All Possible Attributes
  `<INPUT TYPE=type ID="..." LANG="..." CLASS="..." NAME="..." VALUE="..." DISABLED ERROR="..." SRC="..." MD="..." CHECKED SIZE="..." MAXLENGTH="..." MIN=number MAX=number ALIGN=top|middle|bottom|left|right ACCEPT="...">`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<FORM>`
Variations
  Version 2 defines the TYPE attribute values of `text|password|checkbox|radio|submit|reset|hidden|image` The <TEXTAREA> element should be used instead of this INPUT element for multiline input areas. `TYPE=hidden VALUE="..."` is recognized by some browsers, and is used to submit fixed information not entered by the user. `TYPE=image` was introduced in Version 2 and specifies an image, identified by the URL with the new SRC attribute, which, when clicked, performs the submission and sends the X,Y coordinates of the click, similar to ISMAP in the IMG element. Version 2 sets a max limit of 1024 characters on VALUE.

  Version 3 proposes the additional TYPE attribute values of `range|file|scribble`. Version 3 proposes the additional ID, LANG, CLASS, DISABLED, ERROR, MIN, MAX, ACCEPT, and MD attributes. The Version 3 proposed `TYPE=range` uses the proposed MIN and MAX attributes to specify limits to numeric (real or integer) input. The proposed default value is halfway between MIN and MAX. The Version 3 proposed `TYPE=file` permits attaching a file to the submitted output. Version 3 proposes that multiple INPUT elements with `TYPE=file` would be permitted for attaching multiple files. The ACCEPT attribute is proposed to be used to specify a comma separated list of MIME content types of the attached files. The Version 3 proposed `TYPE=scribble` is to allow the user to scribble with a pointing device on top of the image specified with the SRC attribute. The Version 3 proposed DISABLED attribute would display this INPUT, but prohibit user entry/modification. The Version 3 proposed ERROR attribute defines text to be displayed in the event that the entered value for this INPUT is invalid. All elements concerning FORM are Level 2.

## INS

Description
  The INS element changes the character rendering of the contents of the element to logically represent inserted text, for instance in modifications in legal documents.
Minimum Attributes
  `<INS>characters... </INS>`
All Possible Attributes
  `<INS ID="..." LANG="..." CLASS="...">characters... </INS>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The INS element is a Version 3 proposed element. All character definition elements are Level 2.

## ISINDEX

Description
  This element appears to be a precursor to the `<FORM>` element which has more features. When placed in the BODY of the document, it requires the ACTION attribute to point to a cgi-bin program which can handle the query, and produces a simple INPUT field with a prompt of: "`This is a searchable index. Enter search keywords:`" When placed in the HEAD of the document, it informs the browser that the document is an index document and can be examined using a keyword search. The ISINDEX element is usually generated automatically by a server-side script.
Minimum Attributes
  `<ISINDEX>`
All Possible Attributes
  `<ISINDEX ACTION="..." PROMPT="...">`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <FORM> <HEAD> <LI>`
Variations
  The PROMPT attribute is a Netscape extension. ISINDEX is a Level 0 element. The new, more sophisticated FORM element is now used more widely. Version 2 describes ISINDEX as a Level 0 element as part of the HEAD. It does not include it as part of the BODY. Version 3 proposes the PROMPT attribute.

## KBD

Description
  The KBD element changes the character rendering of the contents of the element to logically represent text entered as keyboard input.
Minimum Attributes
  `<KBD>characters... </KBD>`
All Possible Attributes
  `<KBD ID="..." LANG="..." CLASS="...">characters... </KBD>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  While intended to be distinguishable from CODE, so that input and output would be different, most browsers render this the same as CODE, simply as a fixed-width font. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## LANG

Description
  The LANG element is used to change the LANG context from the current context.
Minimum Attributes
  `<LANG>characters... </LANG>`
All Possible Attributes
  `<LANG ID="..." CLASS="...">characters... </LANG>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The LANG element is a Version 3 proposed element. All character definition elements are Level 2.

## LH

Description
  The LH element defines a list header used as a title for a list. Browsers can use this in place of the full list when a mechanism is provided to fold and unfold nested lists.
Minimum Attributes
  `<LH>characters... </LH>`
All Possible Attributes
  `<LH ID="..." LANG="..." CLASS="...">characters... </LH>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `<DL> <OL> <UL>`
Variations
  The LH element is proposed in Version 3 as an optional element at the beginning of lists. It is expected that browsers may render this element in a different style/font than the list itself.

## LI

Description
  The LI element defines a list item. It is rendered differently depending upon the list within which it appears.
Minimum Attributes
  `<LI>characters...`
All Possible Attributes
  `<LI` within UL `TYPE=disk|circle|square` within OL `TYPE=A|a|I|i|i` within OL `VALUE=n>characters...</LI>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I> <P> <UL> <OL> <DIR> <MENU> <DL> <PRE> <BLOCKQUOTE> <FORM> <ISINDEX>`
Allowed In Content Of...
  `<DIR> <MENU> <OL> <UL>`
Variations
  TYPE and VALUE attributes are Netscape extensions. Most browsers assume the list item ends with the beginning of the next list item or the end of the list and do not require the closing tag `</LI>` All list elements are Level 0.

## LINK

Description
  The LINK element is used to indicate a relationship between this document and other documents or objects. Multiple LINK elements may exist in a document. A LINK in document A with an HREF to document/object B with `REL=`relation identifies a relationship that B has to A that A recognizes/authorizes/verifies. A LINK in document B with an HREF to document/object A with `REV=`relation that is the identical relation identifies a desired/expected/claimed relationship of B to document/object A, but must be verified by checking with A. For further description of the LINK attributes, see the A element.
Minimum Attributes
  `<LINK HREF="..." >`
All Possible Attributes
  `<LINK HREF="..." REL="..." REV="..." URN="..." TITLE="..." METHODS="..." >`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<HEAD>`
Variations
  LINK is a Level 0 element. In addition to those mentioned with the A element, Version 3 reserves some relations for REL that are expected to be used for document specific toolbars. Currently these include `Home, ToC, Index, Glossary, Copyright, Up, Next, Previous, Help, Bookmark`. Version 3 also discusses relations for a document banner and style sheets.
Sandia Requirements
  A LINK element in the HEAD to identify the owner of the document responsible for its accuracy is required by Sandia's automated Web tools:
  `<LINK REV="owns" TITLE="Full Name" HREF="mailto:owner-e-mail@sandia.gov">`

  LINK elements are also recommended to identify other individuals and their relationships to this document. The REV value of `made` should be used to identify the author of the document. Suggested values for REV in additional LINK elements are: `approves, editor, publisher.`

  Large documents which are separated into smaller HTML subdocuments should use the LINK element with the REL attribute to identify these relationships. The parent document should identify all subdocuments by:
  `<LINK REL="Subdocument" TITLE="Subdoc Name" HREF="link-url">`
  The subdocument may identify its parent by:
  `<LINK REV="Subdocument" TITLE="Maindoc Name" HREF="link-url">`
  Any Sandia document which is part of a set of HTML subdocuments which form a sequence or hierarchy should include two specific LINK elements identifying the REL values of `next` and `previous`. Only one `next` and one `previous` relationship may be specified in a document.

  Any of the other document relationships mentioned in this Reference Manual may also be used.

## LISTING

Description
  The LISTING element defined a separated multi-line set of text to be rendered as it exists in the source document with the same line breaks.
Minimum Attributes
  `<LISTING>characters... </LISTING>`
All Possible Attributes
  `<LISTING WIDTH="..." >characters... </LISTING>`
Elements Allowed Within...
  `<A> <HR> <BR> <TT> <B> <I> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <FORM> <LI>`
Variations
  Most browsers use fixed-width characters for LISTING text. This element existed in Version 0 and has been replaced by the `<PRE>` element. Version 2 of the standard has declared LISTING as obsolete and some current browsers no longer recognize it.

## MENU

Description
  The MENU element defines an unordered list consisting of a number of separated multi-line `<LI>` elements which may or may not be marked by a bullet or similar symbol. Similar to the `<UL>` element, it is rendered in a more compact manner.
Minimum Attributes
  `<MENU></MENU>`
All Possible Attributes
  `<MENU COMPACT> </MENU>`
Elements Allowed Within...
  `<LI>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <FORM> <LI>`
Variations
  This list type is often rendered identically to UL. The COMPACT attribute of the UL element is more often used than this MENU element. By adding the PLAIN attribute to eliminate the bullets to the UL element, Version 3 proposes to remove the MENU element. All list elements are Level 0.

## META

Description
  The META element is used within the HEAD element to embed document meta-information not defined by other HTML elements. Such information may be extracted by servers/browsers. The HTTP-EQUIV attribute binds the element to an HTTP response header. If not present, the NAME attribute should be used to identify this meta-information and it should not be used within an HTTP response header. If the NAME attribute is not present, the name can be assumed equal to the value of HTTP-EQUIV. The CONTENT attribute defines the meta-information content to be associated with the given name and/or HTTP response header.
Minimum Attributes
  `<META CONTENT="..." >`
All Possible Attributes
  `<META HTTP-EQUIV="..." NAME="..." CONTENT="..." URL="..." >`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<HEAD>`
Variations
  The META element was introduced in Version 2 and is a Level 1 element. Netscape 1.1 has added a automatic refresh capability using the META element by setting the HTTP-EQUIV attribute to `"REFRESH"`, the CONTENT attribute to a number of seconds, and the URL attribute to the file to load which defaults to reloading the same file. The URL attribute is a Netscape extension. Netscape 1.1 also recognizes placing the URL inside the quotes which define the CONTENT value by using a semicolon following the number of seconds, then the URL=http://... text.
Sandia Requirements
  Two META elements are required to identify specific information for Sandia's automated Web tools.
  `<META NAME="REVIEW" CONTENT="DD MMM YYYY">`
  `<META HTTP-EQUIV="KEYWORDS" CONTENT="key1, key2, key3">`
  For large documents split into multiple HTML subdocuments, these META elements should only be included in the HTML document that is the parent of all the subdocuments, usually the Introduction or Table of Contents document.

## NEXTID

Description
  The single attribute `N=` provides the next available identifier for use by automatic hypertext editors. If the NEXTID element is manually entered, it should be alphabetical to avoid conflict with such editors.
Minimum Attributes
  `<NEXTID N="..." >`
All Possible Attributes
  `<NEXTID N="..." >`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<HEAD>`
Variations
  NEXTID is a Level 0 element.

## NOBR

Description
  All text between the start and end of the `NOBR` elements cannot have line breaks inserted between them.
Minimum Attributes
  `<NOBR>characters... </NOBR>`
All Possible Attributes
  `<NOBR>characters... </NOBR>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The NOBR element is a Netscape extension.

## NOTE

Description
  The NOTE element changes the rendering of the contents of the element to logically represent separated notational text. The SRC attribute specifies an image to appear preceding the note.
Minimum Attributes
  `<NOTE>characters... </NOTE>`
All Possible Attributes
  `<NOTE ID="..." LANG="..." CLASS="..." CLEAR=left|right|all|"..." SRC="..." MD="..."</NOTE>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The NOTE element is a Version 3 proposed element. It is expected to typically be rendered indented, without a preceding bullet, symbol, or other graphic. Accompanying style guides are expected to define renderings associated with specific CLASS values. NOTE, CAUTION, and WARNING are expected values for the CLASS attribute.

## OL

Description
  The OL element defines an ordered list consisting of a number of separated multi-line `<LI>` elements, and ordered numerically in some way.
Minimum Attributes
  `<OL></OL>`
All Possible Attributes
  `<OL COMPACT ID="..." LANG="..." CLASS="..." CLEAR=left|right|all|"..." CONTINUE SEQNUM=value START=value TYPE=A|a|I|i|1></OL>`
Elements Allowed Within...
  `<LH> <LI>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <FORM> <LI>`
Variations
  Version 3 proposes the general ID, LANG, CLASS, and CLEAR attributes. The CONTINUE attribute is proposed by Version 3 to continue the numbering from where the previous OL list left off. The SEQNUM attribute is proposed by Version 3 to define a starting number for the list. START is a Netscape extension to do the same thing as SEQNUM. The TYPE attribute is a Netscape extension. Version 3 proposes using associated style sheets and the CLASS attribute to handle these, and other, options to numbering style. All list elements are Level 0.

## OPTION

Description
  The OPTION element identifies a choice in a SELECT element, which in turn is part of the contents of a FORM element. SELECTED specifies that this option is selected by default. If SELECT allows MULTIPLE, then multiple options may be SELECTED. If the VALUE attribute it not present and the OPTION is selected, the OPTION contents is returned upon submission of the FORM. If the VALUE attribute is present and the OPTION is selected, the value of the VALUE attribute is returned instead of the contents.
Minimum Attributes
  `<OPTION>characters...`
All Possible Attributes
  `<OPTION SELECTED DISABLED VALUE="..." ID="..." LANG="..." CLASS="..." ERROR="..." SHAPE="..." >characters... </OPTION>`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<SELECT>`
Variations
  The DISABLED attribute was first proposed with Version 2, is also defined in Version 3, and would display this OPTION, but prohibit user selection/deselection. Version 2 sets a max limit of 1024 characters on VALUE. Version 3 proposes the ID, LANG, CLASS, ERROR, and SHAPE attributes. The Version 3 proposed ERROR attribute defines text to be displayed in the event that selectiing this OPTION is invalid. The Version 3 proposed SHAPE attribute defines the shape of the "hotspot" on the imgage defined by the SRC attribute of the surrounding SELECT element. The proposed values of SHAPE are: `"default"`, `"circle x,y,r"`, `"rect x,y,w,h"`, and `"polygon x1,y1,x2,y2,..."`. All elements concerning FORM are Level 2.

## OVERLAY

Description
  The OVERLAY element is used to overlay one or more images on top of a FIG image. The X and Y attributes identify the offsets from the top left of the FIG where the top left of the overlay will be placed.
Minimum Attributes
  `<OVERLAY SRC="...">`
All Possible Attributes
  `<OVERLAY SRC="..." MD="..." UNITS=pixels|en X=value Y=value WIDTH=value HEIGHT=value IMAGEMAP="...">`
Elements Allowed Within...
Allowed In Content Of...
  `<FIG>`
Variations
  The OVERLAY element is proposed in Version 3 as part of the FIG construct. It is designed to take advantage of the caching system of most browsers for a series of similar images which may only differ by an overlay and the rest is already in cache.

## P

Description
  The P element is used to denote a paragraph break, and separates two blocks of text. Many other elements automatically imply a text separation, such as headings, list elements, blockquotes, etc.
Minimum Attributes
  `<P>characters...`
All Possible Attributes
  `<P ID="name" ALIGN=center|left|right|justify|indent WRAP=on|off NOWRAP CLEAR=left|right|all|"..." LANG="..." CLASS="...">characters... </P>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<ADDRESS> <BLOCKQUOTE> <BODY> <DD> <FORM> <LI>`
Variations
  In Version 1, the `<P>` element was a separator and the `</P>` element was not defined. Version 2 changed the concept to a container and introduced the optional `</P>` element. HTML+ introduced the `ID` and `ALIGN` attributes. The ID attribute is proposed in HTML+ to replace the NAME attribute in the A element to establish internal hyperlink destinations, and ALIGN would define the alignment of the text within the paragraph. Version 3 keeps the optional `</P>` element and both the ID and ALIGN elements, but Version 3 does not currently include `indent` as an option for ALIGN. WRAP would turn off automatic word wrap, leaving text as it appears in the source. Version 3 replaces the WRAP attribute and values with the NOWRAP attribute. The P element is Level 0.

## PERSON

Description
  The PERSON element changes the character rendering of the contents of the element to logically represent the name of people to allow these to be extracted automatically by indexing programs.
Minimum Attributes
  `<PERSON>characters... </PERSON>`
All Possible Attributes
  `<PERSON ID="..." LANG="..." CLASS="...">characters... </PERSON>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The PERSON element is a Version 3 proposed element. All character definition elements are Level 2.

## PLAINTEXT

Description
  The PLAINTEXT element defined a separated multi-line set of text to be rendered as it exists in the source document with the same line breaks. It was designed to ignore all subsequent HTML tags. Therefore, it was always last in a document, allowing the remainder of the document to be presented as text.
Minimum Attributes
  `<PLAINTEXT>characters... </PLAINTEXT>`
All Possible Attributes
  `<PLAINTEXT WIDTH="..." >characters... </PLAINTEXT>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  Most browsers use fixed-width characters for PLAINTEXT text. A few browsers accepted the ending tag, which meant that the ending tag could not exist in the text. This element existed in Version 0 and has been replaced by the `<PRE>` element. Version 2 of the standard has declared PLAINTEXT as obsolete and some current browsers no longer recognize it.

## PRE

Description
  The PRE element defines a separated multi-line set of text to be rendered as it exists in the source document with the same line breaks and spaces. Normal text removes multiple spaces and line breaks in the source.
Minimum Attributes
  `<PRE>characters... </PRE>`
All Possible Attributes
  `<PRE WIDTH="..." ID="..." LANG="..." CLASS="..." CLEAR=left|right|all|"..." >characters... </PRE>`
Elements Allowed Within...
  `<A> <HR> <BR> <TT> <B> <I> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <FORM> <LI>`
Variations
  Most browsers use fixed-width characters for PRE text. The Version 2 specification states that the tab character should position to the next 8 character boundary. Version 3 encourages using the proposed TAB element instead. One typical use of PRE has been for tables, but the Version 3 TABLE element is proposed to fulfill that requirement. The ID, LANG, CLASS, and CLEAR attributes are proposed in Version 3. The attribute WIDTH has been alternatively identified as the maximum number of characters that can be displayed on a single line and the minimum number of characters that the browser should try to insure are displayed on a single line, possibly by selecting a smaller font size. Many browsers ignore the WIDTH attribute, and Version 3 is discussing the possibility of removing it. The PRE element is Level 0.

## Q

Description
  The Q element changes the character rendering of the contents of the element to logically represent a short quotation.
Minimum Attributes
  `<Q>characters... </Q>`
All Possible Attributes
  `<Q ID="..." LANG="..." CLASS="...">characters... </Q>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The Q element is typically shown enclosed in quotations marks as appropriate to the LANG language context. It is a Version 3 proposed element. All character definition elements are Level 2.

## S

Description
  The S element changes the physical rendering of the contents of the element to a font with a strikeout line through the letters.
Minimum Attributes
  `<S>characters... </S>`
All Possible Attributes
  `<S ID="..." LANG="..." CLASS="...">characters... </S>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The S element is proposed in Version 3. This replaces the STRIKE element which was proposed in Version 2. All character definition elements are Level 2.

## SAMP

Description
  The SAMP element changes the character rendering of the contents of the element to logically represent a sequence of literal characters.
Minimum Attributes
  `<SAMP>characters... </SAMP>`
All Possible Attributes
  `<SAMP ID="..." LANG="..." CLASS="...">characters... </SAMP>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  This is usually rendered with a fixed-width font. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## SELECT

Description
  The SELECT element defines a menu of a series of selectable input in a FORM, each identified with the OPTION element. At least one OPTION element is expected within the SELECT contents. NAME is the symbolic name of the field returned to the server on submission. SIZE determines the number of OPTIONS physically visible when the browser displays the FORM. The default selection will be the first OPTION in the SELECT contents. The MULTIPLE attribute, if present, allows multiple selections, and causes no OPTION to be the default.
Minimum Attributes
  `<SELECT NAME="...">characters... </SELECT>`
All Possible Attributes
  `<SELECT NAME="..." SIZE=value MULTIPLE ID="..." LANG="..." CLASS="..." ALIGN=top|middle|bottom|left|right DISABLED ERROR="..." SRC="..." MD="..." WIDTH=value HEIGHT=value UNITS=pixels|em>characters... </SELECT>`
Elements Allowed Within...
  `<OPTION>`
Allowed In Content Of...
  `<FORM>`
Variations
  The ERROR attribute without a value was first introduced with Version 2 and is not widely implemented. Version 3 proposes the ID, LANG, CLASS, ALIGN, DISABLED, ERROR (with a value), SRC, MD, WIDTH, HEIGHT, and UNITS attributes. The Version 3 proposed DISABLED attribute would display this menu, but prohibit user entry/modification. The Version 3 proposed ERROR attribute defines text to be displayed in the event that the current selections for this menu are invalid. Version 3 proposes a SRC attribute to identify a URL for an image to be displayed instead of the OPTION texts for this menu, with each OPTION element identifying its "hotspot" on this image. If SRC is present, the texts would only be used for non-graphical browsers. All elements concerning FORM are Level 2.

## SMALL

Description
  The SMALL element changes the physical rendering of the contents of the element to a smaller font than normal text, if practical.
Minimum Attributes
  `<SMALL>characters... </SMALL>`
All Possible Attributes
  `<SMALL ID="..." LANG="..." CLASS="...">characters... </SMALL>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The SMALL element is proposed in Version 3. All character definition elements are Level 2.

## STRIKE

Description
  The STRIKE element changes the physical rendering of the contents of the element to a font with a strikeout line through the letters.
Minimum Attributes
  `<STRIKE>characters... </STRIKE>`
All Possible Attributes
  `<STRIKE>characters... </STRIKE>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  This is a Version 2 proposed element. (ed: This appears to be an undocumented extension which works in Netscape. Anyone try this with other browsers?) This is replaced in Version 3 with the <S> element.

## STRONG

Description
  The STRONG element changes the character rendering of the contents of the element to logically strengthen the text.
Minimum Attributes
  `<STRONG>characters... </STRONG>`
All Possible Attributes
  `<STRONG ID="..." LANG="..." CLASS="...">characters... </STRONG>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  This is usually rendered as bold. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## SUB

Description
  The SUB element changes the physical rendering of the contents of the element to a subscripted position.
Minimum Attributes
  `<SUB>characters... </SUB>`
All Possible Attributes
  `<SUB ID="..." LANG="..." CLASS="...">characters... </SUB>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The SUB element is proposed in Version 2. No font size change was implied in Version 2, but Version 3 states that the font size shall be smaller than normal, if practical. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## SUP

Description
  The SUP element changes the physical rendering of the contents of the element to a superscripted position.
Minimum Attributes
  `<SUP>characters... </SUP>`
All Possible Attributes
  `<SUP ID="..." LANG="..." CLASS="...">characters... </SUP>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The SUP element is proposed in Version 2. No font size change was implied in Version 2, but Version 3 states that the font size shall be smaller than normal, if practical. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## TAB

Description
  The TAB element aligns the following text according to a defined horizontal position. A TAB position can be defined by the ID attribute. Text is positioned using the TO and/or ALIGN attributes, or the INDENT attribute.
Minimum Attributes
  `<TAB>characters...`
All Possible Attributes
  `<TAB ID="..." INDENT=ens TO="..." ALIGN=left|center|right|decimal DP="...">characters...`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The TAB element is proposed in Version 3.

## TABLE

Description
  The TABLE element defines a series of rows of table cell elements. The contents of the TABLE element expects an optional CAPTION element, followed by a series of TR elements, which in turn are followed by a series of optional TH header elements and/or TD data elements.
Minimum Attributes
  `<TABLE></TABLE>`
All Possible Attributes
  `<TABLE ID="..." LANG="..." CLASS="..." CLEAR=left|right|all|"..." NOFLOW ALIGN=left|right|center|justify|bleedleft|bleedright UNITS=en|relative|pixels COLSPEC="..." DP="..." WIDTH=value BORDER=value NOWRAP></TABLE>`
Elements Allowed Within...
  `<CAPTION> <TR> <TABLE>
  -others TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The TABLE element is proposed in Version 3. Consistent with the nature of HTML, it defines the logical contents of cells and their row/column location, rather than a physical layout which is left as a function of the browser. Details of the appearence of the table, along with the size of margins around cells, even perhaps ruling and shading, might be controlled by associated style sheets, proposed in Version 3. This element is an extension in Netscape 1.1. Having a value possible for the BORDER attribute is a Netscape extension. The attributes CELLSPACING and CELLPADDING are Netscape extensions. (ed.The exact behavior caused by the WIDTH appears to be different in the description of Version 3 and Netscape.)

## TD

Description
  The TD element defines a data cell as part of the TABLE construct.
Minimum Attributes
  `<TD>`
All Possible Attributes
  `<TD ID="..." LANG="..." CLASS="..." COLSPAN=value ROWSPAN=value ALIGN=left|right|center|justify|decimal DP="..." VALIGN=top|middle|bottom|baseline NOWRAP AXIS="..." AXES="..." WIDTH=value>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `<TABLE>`
Variations
  The TD element is proposed in Version 3 as part of the TABLE construct. A browser is to assume the table cell ends with the beginning of the next table cell or the beginning of another table row or the end of the table and thus a closing tag is not defined. This element is an extension in Netscape 1.1. The values `justify|decimal` for the ALIGN attribute do not yet exist in Netscape. The WIDTH attribute is a Netscape extension.

## TEXTAREA

Description
  The TEXTAREA element is used to specify a multiline input field as part of the contents in a FORM element. `NAME` defines the symbolic name of the field returned to the server on submission. The characters between the opening and closing tags define the text to be initially displayed in the textarea, and the default text to be returned, normally null. Only ASCII text is allowed as characters, and newlines are respected. `ROWS` and `COLS` define the physical size of the displayed input field in numbers of characters.
Minimum Attributes
  `<TEXTAREA NAME="..." ROWS="..." COLS="..."> </TEXTAREA>`
All Possible Attributes
  `<TEXTAREA NAME="..." ROWS="..." COLS="..." ID="..." LANG="..." CLASS="..." ALIGN=top|middle|bottom|left|right DISABLED ERROR="...">characters... </TEXTAREA>`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<FORM>`
Variations
  Version 3 proposes the ID, LANG, CLASS, ALIGN, DISABLED, and ERROR attributes. The Version 3 proposed DISABLED attribute would display this TEXTAREA, but prohibit user entry/modification. The Version 3 proposed ERROR attribute defines text to be displayed in the event that the entered value for this TEXTAREA is invalid. All elements concerning FORM are Level 2.

## TH

Description
  The TH element defines a header cell as part of the TABLE construct. The browser should render the table to cause some difference between TH elements and TD elements.
Minimum Attributes
  `<TH>`
All Possible Attributes
  `<TH ID="..." LANG="..." CLASS="..." COLSPAN=value ROWSPAN=value ALIGN=left|right|center|justify|decimal DP="..." VALIGN=top|middle|bottom|baseline NOWRAP AXIS="..." AXES="..." WIDTH=value>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `<TABLE>`
Variations
  The TH element is proposed in Version 3 as part of the TABLE construct. A browser is to assume the table cell ends with the beginning of the next table cell or the beginning of another table row or the end of the table and thus a closing tag is not defined. This element is an extension in Netscape 1.1. The values `justify|decimal` for the ALIGN attribute do not yet exist in Netscape. The WIDTH attribute is a Netscape extension. Netscape renders TH elements in a bold font, but otherwise identical to TD elements.

## TITLE

Description
  The TITLE is not part of the document text. Often the title is used by a browser to label the display window. Some Web search engines only search the title of Web pages. Therefore the text of the TITLE should be kept short (usually less than 64 characters) but sufficient to identify the document.
Minimum Attributes
  `<TITLE>characters... </TITLE>`
All Possible Attributes
  `<TITLE>characters... </TITLE>`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<HEAD>`
Variations
  Some browsers will truncate titles to a length they can handle. TITLE is a Level 0 element.
Sandia Requirements
  The TITLE element is required to include a short, uniquely descriptive document title.

## TR

Description
  The TR element defines a row as part of the TABLE construct. The contents of the TR element is expected to contain at least one of either the TH element or the TD element.
Minimum Attributes
  `<TR>`
All Possible Attributes
  `<TR ID="..." LANG="..." CLASS="..." ALIGN=left|right|center|justify|decimal DP="..." VALIGN=top|middle|bottom|baseline NOWRAP>`
Elements Allowed Within...
  `<TD> <TH>
  -others TBD-`
Allowed In Content Of...
  `<TABLE>`
Variations
  The TR element is proposed in Version 3. A browser is to assume the table row ends with the beginning of the next table row or the end of the table and thus a closing tag is not defined. Version 3 proposes that browsers should tolerate the absence of the first TR in a table. This element is an extension in Netscape 1.1. The values `justify|decimal` for the ALIGN attribute do not yet exist in Netscape.

## TT

Description
  The TT element changes the physical rendering of the contents of the element to a fixed width typewriter font.
Minimum Attributes
  `<TT>characters... </TT>`
All Possible Attributes
  `<TT ID="..." LANG="..." CLASS="...">characters... </TT>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## U

Description
  The U element changes the physical rendering of the contents of the element to an underlined font.
Minimum Attributes
  `<U>characters... </U>`
All Possible Attributes
  `<U ID="..." LANG="..." CLASS="...">characters... </U>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  The U element is proposed in the Version 2 specification but is not widely implemented. The ID, LANG, and CLASS attributes are proposed in Version 3. It is often rendered in italic or slanted rather than underlined. All character definition elements are Level 2.

## UL

Description
  The UL element defines an unordered list consisting of a number of separated multi-line `<LI>` elements, and usually marked by a bullet or similar symbol.
Minimum Attributes
  `<UL></UL>`
All Possible Attributes
  `<UL COMPACT ID="..." LANG="..." CLASS="..." CLEAR=left|right|all|"..." PLAIN SRC="..." MD="..." DINGBAT="..." WRAP=vert|horiz TYPE=disk|circle|square> </UL>`
Elements Allowed Within...
  `<LH> <LI>`
Allowed In Content Of...
  `<BLOCKQUOTE> <BODY> <DD> <FORM> <LI>`
Variations
  Nested UL lists are usually rendered more indented with differing bullets or symbols. Version 3 proposes the ID, LANG, CLASS, CLEAR, PLAIN, SRC, MD, DINGBAT, and WRAP attributes. The TYPE attribute is a current Netscape extension. Version 3 proposes to replace it with the SRC and DINGBAT attributes to point to general server and browser images respectively. Specifying `<UL PLAIN>` to eliminate the bullets is proposed by Version 3 as a replacement for the MENU element. Specifying `<UL PLAIN WRAP=HORIZ>` is proposed by Version 3 as a replacement for the DIR element. The browser may dynamically determine the appropriate number of columns. All list elements are Level 0.

## VAR

Description
  The VAR element changes the character rendering of the contents of the element to logically represent a variable name.
Minimum Attributes
  `<VAR>characters... </VAR>`
All Possible Attributes
  `<VAR ID="..." LANG="..." CLASS="...">characters... </VAR>`
Elements Allowed Within...
  `<A> <IMG> <BR> <EM> <STRONG> <CODE> <SAMP> <KBD> <VAR> <CITE> <TT> <B> <I>`
Allowed In Content Of...
  `<A> <ADDRESS> <B> <CITE> <CODE> <DD> <DT> <EM> <H1> <H2> <H3> <H4> <H5> <H6> <I> <KBD> <LI> <P> <PRE> <SAMP> <STRONG> <TT> <VAR>`
Variations
  This is usually rendered in italics. The ID, LANG, and CLASS attributes are proposed in Version 3. All character definition elements are Level 2.

## WBR

Description
  The WBR element exists to force the possibility of a word break in a no-break section.
Minimum Attributes
  `<WBR>`
All Possible Attributes
  `<WBR>`
Elements Allowed Within...
  ``
Allowed In Content Of...
  `<NOBR>`
Variations
  The NOBR element is a Netscape extension.

## XMP

Description
  The XMP element defined a separated multi-line set of text to be rendered as it exists in the source document with the same line breaks.
Minimum Attributes
  `<XMP>characters... </XMP>`
All Possible Attributes
  `<XMP WIDTH="..." >characters... </XMP>`
Elements Allowed Within...
  `-TBD-`
Allowed In Content Of...
  `-TBD-`
Variations
  Most browsers use fixed-width characters for XMP text. This element existed in Version 0 and has been replaced by the `<PRE>` element. Version 2 of the standard has declared XMP as obsolete and some current browsers no longer recognize it.

## Uniform Resource Locator (URL)

Description
  Uniform Resource Locators (URL) let you specify how to reach an Internet resource. They consist of four basic parts: `aaaa://bbb.bbb.bbb/ccc/ccc/ccc?ddd`
  `aaaa:` The access method.
    This specifies the mechanism to be used by the browser to communicate with the resource. Mechanism codes must be registered to be widely recognized. An X500 mechanism, as well as WHOIS, and Network Database mechanisms are under study. Currently recogized mechanisms include:
    `http:` HyperText Transfer Protocol
      This is the most commonly used access method. It requires a program running on the destination computer that understands and responds to this protocol. The file retrieved might be an HTML file, a graphic file, a sound file, an animation sequence file, a file to be executed by the server (e.g. cgi-bin files), or a word processing file. Whether the file retrieved can be handled depends on the browser.
    `https:` HyperText Transfer Protocol
      This is a variation on the standard access method. (ed: I am still researching/working on this definition.)
    `file:` Local File Access
      This method causes the browser to load a file from the locally accessible disk system. This is commonly used to preview Web pages being developed on a computer that has a browser, but does not have a server.
    `ftp:` File Transport Protocol
      This method uses normal Internet FTP to retrieve a file. Most browsers will ask for a location/name on the local disk system to store the file.
    `mailto:` E-Mail Form
      The argument following the access code is the destination e-mail address. If the browser understands this access code, the browser will automatically generate an input FORM for entering the e-mail message. It may also accept additional arguments for default "Subject:" etc. Most Version 2 browsers now handle this access code. Note that any special characters in an e-mail address (e.g. "%") must be URL converted (e.g. "%25")
    `news:` USENET News
      Only argument following the access code is the group or article name.
    `nntp:` Local Network News Transport Protocol
      --TBD--
    `wais:` Wide Area Information Servers
      --TBD--
    `gopher:` GOPHER
      --TBD--
    `telnet:` TELNET
      The arguments following the access code are the login arguments to the telnet session as `user[:password]@host`.
    `cid:` Content identifiers for MIME body part
      --TBD--
    `mid:` Message identifiers for electronic mail
      --TBD--
    `afs:` AFS File Access
      --TBD--
    `prospero:` Prospero Link
      --TBD--
    `x-exec:` Executable Program
      --TBD--
  `//bbb.bbb.bbb` The Internet node
    This specifies the node on the Internet where the file is located. If not included, it defaults to the computer on which the browser is running, which is appropriate for access method `file:` The node may optionally be followed by a colon and the port number. Most browsers default to port 80, which is also what most servers use to reply to the browser. For access method `ftp:` the node name may take the form `//user[:password]@host`. Without a user name, the user `anonymous` is used.
  `/ccc/ccc/ccc` The file path
    This is the pathname of the file to be retrieved, including the directories, subdirectories, and filename. A server can specify the "root" of the directory system recognized by an access type as some subordinate directory. This restricts access to files subordinate to that directory.
  `?ddd` Arguments
    Depending upon the access method, and the file accessed, characters can follow the file name, separated by some pre-defined special character (e.g. "#", "?", "&", etc.). This information can then be used by the access method as additional arguments for the access. In the case of access method `http:` where the file is an executable cgi-bin program registered with the server, the arguments are passed to the program.
Further References
  `http://www.w3.org/hypertext/WWW/Addressing/URL/5_BNF.html`
    BNF Specification of URLs.

## Special Characters

Minimum Attributes
  The leading ampersand and trailing semi-colon are required. These main four special characters are specifically included in the Version 2 specification.
  `&lt;`
    < (less than sign)
  `&gt;`
    > (greater than sign)
  `&amp;`
    & (The ampersand sign itself)
  `&quot;`
    " (quote character)
Variations
  The `&quot;` is specified as being either a single or double quote, but most browsers render it as a double quote. All the remaining special character entity names are listed in `http://www.sandia.gov/sci_compute/symbols.html` Not all of those special characters are recognized by all browsers. The entity name of many of the proposed characters is case sensitive and intentionally includes mixed case which must be entered exactly as specified. Since most browsers are insensitive to case for HTML names, many browsers do not require the entity names of the main four special characters to be lower case.
  `&#nn;`
    ISO Latin-1 character number "nn" (the number sign "#" is required)

  The following document displays all the ISO Latin-1 characters and can be used to see what they will produce on your browser. `http://www.sandia.gov/sci_compute/iso_symbol.html`

  The Version 2 Specification recommends referencing special characters with the entity names described above instead of using these numeric ISO Latin-1 code entity names.

## Standard Icons

Minimum Attributes
  A standard set of icon names is expected to be recognized by the browser for use by the DINGBAT attribute in the H1, H2, H3, H4, H5, H6, and UL elements or as hypertext links to an image. The browser may either display them from local code/files, or may expand them to URLs. Similar to special characters, these names are case sensitive, and are enclosed in the "`&`" and "`;`" characters.
Variations
  Standard icons are proposed in Version 3. Browsers are likely to provide extensions to the standard set of icons. The following document lists the currently proposed icon entity names: `http://www.sandia.gov/sci_compute/icons.html`

## Disclaimer

This document is a merging of information from a variety of other documents obtained from the WWW. Everything in this document was copied or borrowed from some other Web document, most of which are recognized in the Acknowledgements below. While there exist a number of Beginner's Guides to writing HTML, verbal descriptions of parts of HTML, and technical Document Type Definitions (DTD) specifications of the language, I could not find a concise reference document for the language. This reference document is an attempt to fill that gap. While I have made every effort to be complete, that is always an unattained goal, especially since I am not involved in the development or standardization of this language. The information in this document is the best I have been able to find. If I have something missing or wrong, please send me e-mail with a definitive source so that I can keep this document as current, accurate, and complete as possible.

The mention, or lack of mention, of any HTML browser product, service, or company shall not be construed as either a positive or negative endorsement of or comment about such product, service, or company. At most it expresses my personal knowledge or ignorance of the information. This document is neither intended to be nor capable of being an exhaustive discussion of browser capabilities. It is focused on Sandia's internal needs. Please also refer to the standard Sandia disclaimer of liability.

## Acknowledgements

Thanks to the following sources from which I have liberally borrowed.

`http://www.w3.org/hypertext/WWW/MarkUp/MarkUp.html`
  The general home page for HTML information at WWW.
`http://www.w3.org/hypertext/WWW/MarkUp/html-spec/L2index.html`
  This alphabetical listing of HTML elements for Version 2, constructed by Dan Connolly, formed the original structure of this document. Prior to Dan Connolly's move to World Wide Web Consortium (W3C) at MIT, this reference was: `http://www.hal.com/users/connolly/html-spec/htmlindex.html`
`http://www.ucc.ie/~pflynn/books/htmlcard.html`
  A quick reference card to the HTML elements, organized by logical function. This card appears in printed form in Spinning the Web (1-850-32141-8) by Andrew Ford, and The WorldWideWeb Handbook (1-850-32205-8) by Peter Flynn, both published by International Thomson Computer Press.
`http://lcweb.loc.gov/global/html.html`
  The Library of Congress index of links about HTML.
`http://www.utirc.utoronto.ca/HTMLdocs/NewHTML/htmlindex.html`
  A draft of the upcoming book on HTML Documentation by Ian Grahm.
`http://www.ncsa.uiuc.edu/SDG/Software/Mosaic/Docs/fill-out-forms/overview.html`
  Documentation of Mosiac for X version 2.0 fill-out form support.
`http://www.ncsa.uiuc.edu/General/Internet/WWW/HTMLPrimer.html`
  The HTML Primer developed by NCAR.
`http://www.w3.org/hypertext/WWW/MarkUp/HTML.html`
  The draft 1.2 of Internet MIME Content Type (RFC 1341) which expired 13 Jan 1994. It is a description of Version 1 HTML written by Tim Berners-Lee and Daniel Connolly.
`http://kuhttp.cc.ukans.edu/lynx_help/HTML_quick.html`
  A quick reference to HTML Version 1 by Michael Grobe.
`http://www.w3.org/hypertext/WWW/MarkUp/html-spec/html.dtd`
  The Document Type Definition (DTD) of the Version 2 specification for HTML. Prior to Dan Connolly's move to World Wide Web Consortium (W3C) at MIT, this reference was: `http://www.hal.com/users/connolly/html-spec/html-pubtext.html`
`http://www.ics.uci.edu/pub/ietf/html/html2/index.html`
  HTML Version 2 as of 29 Nov 1994 as an Internet Media Type (RFC 1590) and MIME Content Type (RFC 1521) written by Tim Berners-Lee and Daniel Connolly.
`http://www.w3.org/hypertext/WWW/MarkUp/Text.html`
  The syntax of the text of HTML.
`http://home.mcom.com/home/services_docs/html-extensions.html`
  The description of the extensions to HTML used by Netscape, Version 1.0.
`http://www.netscape.com/assist/net_sites/html_extensions.html`
  The description of the extensions to HTML used by Netscape, Version 1.1.
`http://hoohoo.ncsa.uiuc.edu/cgi/overview.html`
  This document appears to be a definitive reference to the Common Gateway Interface, which describes the structure of cgi-bin programs. These programs are required for the ISMAP attribute of the IMG element, as well as for processing FORM element input.
`http://hoohoo.ncsa.uiuc.edu/docs/setup/admin/Imagemap.html`
  This document discusses, with examples, how the NCSA image map utility works. This is a cgi-bin program that is useful with the ISMAP attribute on the IMG element.
`http://hoohoo.ncsa.uiuc.edu/docs/setup/admin/NewImagemap.html`
  This document discusses, with examples, how the newer version of the NCSA image map utility works. This is a cgi-bin program that is useful with the ISMAP attribute on the IMG element. This newer imagemap program is much more versatile than the original version distributed with the NCSA HTTP1.3 server. The document describes the advantages of the new program, and provides directions to the source code.
`http://www.w3.org/hypertext/WWW/MarkUp/HTMLPlus/htmlplus_1.html`
  HTML+ (a superset of Version 2, and the precursor to Version 3) as of 8 Nov 1993, by David Raggett. Includes some interesting possibilities.
`http://www.w3.org/hypertext/WWW/Arena/tour/start.html`
  An overview of the proposed features of Version 3, and identification of those proposals likely to be deferred until Version 3.1. Also identifies access to a test browser designed to display the new Version 3.0 features as part of the review process.
`http://www.hpl.hp.co.uk/people/dsr/html/CoverPage.html`
  A current draft of the text for a proposed Version 3 as an Internet RFC by David Raggett. This link is identical to `http://www.hpl.hp.co.uk/people/dsr/html3/CoverPage.html`
`http://ppewww.ph.gla.ac.uk/~flavell/iso8859/iso8859-1.html`
  An excellent analysis of the relationship of the ISO8859 Latin-1 character set with HTML entities, including representational tables.
`http://www.willamette.edu/html-composition/strict-html.html`
  This is my personal favorite of the many documents describing how to write good HTML, including "Common Errors" and "Things to Avoid".
`http://www.w3.org/hypertext/WWW/Provider/Style/Overview.html`
  The Style Guide at the World Wide Web Consortium (W3C) at MIT, written by Tim Berners-Lee.

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