Introduction

The HyperText Markup Language (HTML) is a simple data format used to create hypertext documents that are portable from one platform to another. HTML documents are SGML documents with generic semantics that are appropriate for representing information from a wide range of domains.

As HTML is an application of SGML, this specification assumes a working knowledge of [SGML].

Scope

HTML has been in use by the World-Wide Web (WWW) global information initiative since 1990. Previously, informal documentation on HTML has been available from a number of sources on the Internet. This specification brings together, clarifies, and formalizes a set of features that roughly corresponds to the capabilities of HTML in common use prior to June 1994. A number of new features to HTML are being proposed and experimented in the Internet community.

This document thus defines a HTML 2.0 (to distinguish it from the previous informal specifications). Future (generally upwardly compatible) versions of HTML with new features will be released with higher version numbers.

HTML is an application of ISO Standard 8879:1986 Information Processing Text and Office Systems; Standard Generalized Markup Language (SGML). The HTML Document Type Definition (DTD) is a formal definition of the HTML syntax in terms of SGML.

This specification also defines HTML as an Internet Media Type[IMEDIA] and MIME Content Type[MIME] called `text/html'. As such, it defines the semantics of the HTML syntax and how that syntax should be interpreted by user agents.

Conformance

This specification governs the syntax of HTML documents and aspects of the behavior of HTML user agents.

Documents

A document is a conforming HTML document if:

• It is a conforming SGML document, and it conforms to the HTML DTD (see section HTML DTD). (1)
• It conforms to the application conventions in this specification. For example, the value of the HREF attribute of the A element must conform to the URI syntax.
• Its document character set includes [ISO-8859-1] and agrees with [ISO-10646]; that is, each code position listed in section The HTML Coded Character Set is included, and each code position in the document character set is mapped to the same character as [ISO-10646] designates for that code position. (2)

Feature Test Entities

The HTML DTD defines a standard HTML document type and several variations, by way of feature test entities. Feature test entities are declarations in the HTML DTD that control the inclusion or exclusion of portions of the DTD.

HTML.Recommended

Certain features of the language are necessary for compatibility with widespread usage, but they may compromise the structural integrity of a document. This feature test entity selects a more prescriptive document type definition that eliminates those features. It is set to `IGNORE' by default. For example, in order to preserve the structure of a document, an editing user agent may translate HTML documents to the recommended subset, or it may require that the documents be in the recommended subset for import.

HTML.Deprecated

Certain features of the language are necessary for compatibility with earlier versions of the specification, but they tend to be used and implemented inconsistently, and their use is deprecated. This feature test entity enables a document type definition that allows these features. It is set to `INCLUDE' by default. Documents generated by translation software or editing software should not contain deprecated idioms.

User Agents

An HTML user agent conforms to this specification if:

• It parses the characters of an HTML document into data characters and markup according to [SGML]. (3)
• It supports the `ISO-8859-1' character encoding scheme and processes each character in the ISO Latin Alphabet No. 1 as specified in section The HTML Document Character Set. (4)
• It behaves identically for documents whose parsed token sequences are identical. For example, comments and the whitespace in tags disappear during tokenization, and hence they do not influence the behavior of conforming user agents.
• It allows the user to traverse (or at least attempt to traverse, resources permitting) all hyperlinks from A elements in an HTML document.

An HTML user agent is a level 2 user agent if, additionally:

• It allows the user to express all form field values specified in an HTML document and to (attempt to) submit the values as requests to information services.