1. 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].
1.1. 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.
1.2. Conformance
This specification governs the syntax of HTML documents and aspects
of the behavior of HTML user agents.
1.2.1. Documents
A document is a conforming HTML document if:
* It is a conforming SGML document, and it conforms to the
HTML DTD (see 9.1, "HTML DTD").
NOTE - There are a number of syntactic idioms that
are not supported or are supported inconsistently in
some historical user agent implementations. These
idioms are identified in notes like this throughout
this specification.
* 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 13, "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.
NOTE - The document character set is somewhat
independent of the character encoding scheme used to
represent a document. For example, the `ISO-2022-JP'
character encoding scheme can be used for HTML
documents, since its repertoire is a subset of the
[ISO-10646] repertoire. The critical distinction is
that numeric character references agree with
[ISO-10646] regardless of how the document is
encoded.
1.2.2. 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.
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].
NOTE - In the interest of robustness and
extensibility, there are a number of widely deployed
conventions for handling non-conforming documents.
See 4.2.1, "Undeclared Markup Error Handling" for
details.
* It supports the `ISO-8859-1' character encoding scheme and
processes each character in the ISO Latin Alphabet No. 1 as
specified in 6.1, "The HTML Document Character Set".
NOTE - To support non-western writing systems, HTML
user agents are encouraged to support
`ISO-10646-UCS-2' or similar character encoding
schemes and as much of the character repertoire of
[ISO-10646] as is practical.
* 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.
