1. About the HTML 4Specification

1.1 How the specification is organized

This specification is divided into the following sections:

Sections 2 and 3: Introduction to HTML 4

The introduction describes HTML's place in the scheme of the World WideWeb, provides a brief history of the development of HTML, highlights what canbe done with HTML 4, and provides some HTML authoring tips.

The brief SGML tutorial gives readers some understanding of HTML'srelationship to SGML and gives summary information on how to read the HTMLDocument Type Definition (DTD).

Sections 4 - 24: HTML 4 reference manual

The bulk of the reference manual consists of the HTML language reference,which defines all elements and attributes of the language.

This document has been organized by topic rather than by the grammar ofHTML. Topics are grouped into three categories: structure, presentation, andinteractivity. Although it is not easy to divide HTML constructs perfectly intothese three categories, the model reflects the HTML Working Group's experiencethat separating a document's structure from its presentation produces moreeffective and maintainable documents.

The language reference consists of the following information:

• What characters may appear in anHTML document.

• Basic data types of an HTML document.

• Elements that govern the structure of an HTML document, including text, lists, tables, links, and included objects, images, andapplets.

• Elements that govern the presentation of an HTML document, including style sheets, fonts, colors, rules, and other visualpresentation, and frames for multi-windowedpresentations.

• Elements that govern interactivity with an HTML document, including forms for user input and scripts for active documents.

• The SGML formal definition of HTML:

  • The SGML declaration of HTML.
  • Three DTDs: strict, transitional, and frameset.
  • The list of character references.

Appendixes

The first appendix contains information about changes from HTML 3.2 to help authors andimplementors with the transition to HTML 4, and changes from the 18 December 1997specification. The second appendix contains performance and implementation notes, and is primarily intended to helpimplementors create user agents for HTML 4.

References

A list of normative and informative references.

Indexes

Three indexes give readers rapid access to the definition of key concepts, elementsand attributes.

1.2 Document conventions

This document has been written with two types of readers in mind: authorsand implementors. We hope the specification will provide authors with the toolsthey need to write efficient, attractive, and accessible documents, withoutover-exposing them to HTML's implementation details. Implementors, however,should find all they need to build conforming user agents.

The specification may be approached in several ways:

• Read from beginning to end. The specification begins with ageneral presentation of HTML and becomes more and more technical and specifictowards the end.

• Quick access to information. In order to get informationabout syntax and semantics as quickly as possible, the online version of thespecification includes the following features:
  1. Every reference to an element or attribute is linked to its definition inthe specification. Each element or attribute is defined in only onelocation.
  2. Every page includes links to the indexes, so you never are more than twolinks away from finding the definition of an element or attribute.

  3. The front pages of each section of the language reference manual extend theinitial table of contents with more detail about that section.

1.2.1 Elements and attributes

Element names are written in uppercase letters (e.g., BODY). Attribute namesare written in lowercase letters (e.g., lang, onsubmit). Recall that in HTML,element and attribute names are case-insensitive; the convention is meant toencourage readability.

Element and attribute names in this document have been marked up and may berendered specially by some user agents.

Each attribute definition specifies the type of its value. If the typeallows a small set of possible values, the definition lists the set of values,separated by a bar (|).

After the type information, each attribute definition indicates thecase-sensitivity of its values, between square brackets ("[]"). See the sectionon case information for details.

1.2.2 Notes and examples

Informative notes are emphasized to stand out from surrounding text and maybe rendered specially by some user agents.

All examples illustrating deprecatedusage are marked as "DEPRECATED EXAMPLE". Deprecated examples also includerecommended alternate solutions. All examples that illustrates illegal usageare clearly marked "ILLEGAL EXAMPLE".

Examples and notes have been marked up and may be rendered specially by someuser agents.

1.3 Acknowledgments

Thanks to everyone who has helped to author the working drafts that wentinto the HTML 4 specification, and to all those who have sent suggestions andcorrections.

Many thanks to the Web Accessibility Initiative task force (WAI HC group)for their work on improving the accessibility of HTML and to T.V. Raman (Adobe)for his early work on developing accessible forms.

The authors of this specification, the members of the W3C HTML Working Group, deserve muchapplause for their diligent review of this document, their constructivecomments, and their hard work: John D. Burger (MITRE), Steve Byrne (JavaSoft),Martin J. Dürst (University of Zurich), Daniel Glazman (Electricitéde France), Scott Isaacs (Microsoft), Murray Maloney (GRIF), Steven Pemberton(CWI), Robert Pernett (Lotus), Jared Sorensen (Novell), Powell Smith (IBM),Robert Stevahn (HP), Ed Tecot (Microsoft), Jeffrey Veen (HotWired), Mike Wexler(Adobe), Misha Wolf (Reuters), and Lauren Wood (SoftQuad).

Thank you Dan Connolly (W3C) for rigorous and bountiful input as part-timeeditor and thoughtful guidance as chairman of the HTML Working Group. Thank youSally Khudairi (W3C) for your indispensable work on press releases.

Thanks to David M. Abrahamson and Roger Price for their careful reading ofthe specification and constructive comments.

Thanks to Jan Kärrman, author of html2ps for helping so much increating the Postscript version of the specification.

Of particular help from the W3C at Sophia-Antipolis were Janet Bertot, BertBos, Stephane Boyera, Daniel Dardailler, Yves Lafon, Håkon Lie, ChrisLilley, and Colas Nahaboo (Bull).

Lastly, thanks to Tim Berners-Lee without whom none of this would have beenpossible.

1.3.1 Acknowledgments for the current revision

Many thanks to Shane McCarron for tracking errata for this revision of thespecification.

1.4 Copyright Notice

For information about copyrights, please refer to the W3C IntellectualProperty Notice, the W3CDocument Notice, and the W3C IPRSoftware Notice.