📄 rfc1866.txt
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Network Working Group T. Berners-Lee
Request for Comments: 1866 MIT/W3C
Category: Standards Track D. Connolly
November 1995
Hypertext Markup Language - 2.0
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
The Hypertext Markup Language (HTML) is a simple markup language used
to create hypertext documents that are platform independent. HTML
documents are SGML documents with generic semantics that are
appropriate for representing information from a wide range of
domains. HTML markup can represent hypertext news, mail,
documentation, and hypermedia; menus of options; database query
results; simple structured documents with in-lined graphics; and
hypertext views of existing bodies of information.
HTML has been in use by the World Wide Web (WWW) global information
initiative since 1990. This specification roughly corresponds to the
capabilities of HTML in common use prior to June 1994. HTML is an
application of ISO Standard 8879:1986 Information Processing Text and
Office Systems; Standard Generalized Markup Language (SGML).
The "text/html" Internet Media Type (RFC 1590) and MIME Content Type
(RFC 1521) is defined by this specification.
Table of Contents
1. Introduction ........................................... 2
1.1 Scope .................................................. 3
1.2 Conformance ............................................ 3
2. Terms .................................................. 6
3. HTML as an Application of SGML .........................10
3.1 SGML Documents .........................................10
3.2 HTML Lexical Syntax ................................... 12
3.3 HTML Public Text Identifiers .......................... 17
3.4 Example HTML Document ................................. 17
4. HTML as an Internet Media Type ........................ 18
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RFC 1866 Hypertext Markup Language - 2.0 November 1995
4.1 text/html media type .................................. 18
4.2 HTML Document Representation .......................... 19
5. Document Structure .................................... 20
5.1 Document Element: HTML ................................ 21
5.2 Head: HEAD ............................................ 21
5.3 Body: BODY ............................................ 24
5.4 Headings: H1 ... H6 ................................... 24
5.5 Block Structuring Elements ............................ 25
5.6 List Elements ......................................... 28
5.7 Phrase Markup ......................................... 30
5.8 Line Break: BR ........................................ 34
5.9 Horizontal Rule: HR ................................... 34
5.10 Image: IMG ............................................ 34
6. Characters, Words, and Paragraphs ..................... 35
6.1 The HTML Document Character Set ....................... 36
7. Hyperlinks ............................................ 36
7.1 Accessing Resources ................................... 37
7.2 Activation of Hyperlinks .............................. 38
7.3 Simultaneous Presentation of Image Resources .......... 38
7.4 Fragment Identifiers .................................. 38
7.5 Queries and Indexes ................................... 39
7.6 Image Maps ............................................ 39
8. Forms ................................................. 40
8.1 Form Elements ......................................... 40
8.2 Form Submission ....................................... 45
9. HTML Public Text ...................................... 49
9.1 HTML DTD .............................................. 49
9.2 Strict HTML DTD ....................................... 61
9.3 Level 1 HTML DTD ...................................... 62
9.4 Strict Level 1 HTML DTD ............................... 63
9.5 SGML Declaration for HTML ............................. 64
9.6 Sample SGML Open Entity Catalog for HTML .............. 65
9.7 Character Entity Sets ................................. 66
10. Security Considerations ............................... 69
11. References ............................................ 69
12. Acknowledgments ....................................... 71
12.1 Authors' Addresses .................................... 71
13. The HTML Coded Character Set .......................... 72
14. Proposed Entities ..................................... 75
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.
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RFC 1866 Hypertext Markup Language - 2.0 November 1995
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
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RFC 1866 Hypertext Markup Language - 2.0 November 1995
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.
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RFC 1866 Hypertext Markup Language - 2.0 November 1995
Documents generated by translation software or editing
software should not contain deprecated idioms.
1.2.3. 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].
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.
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RFC 1866 Hypertext Markup Language - 2.0 November 1995
2. Terms
absolute URI
a URI in absolute form; for example, as per [URL]
anchor
one of two ends of a hyperlink; typically, a phrase
marked as an <A> element.
base URI
an absolute URI used in combination with a relative URI
to determine another absolute URI.
character
An atom of information, for example a letter or a digit.
Graphic characters have associated glyphs, whereas
control characters have associated processing semantics.
character encoding
scheme
A function whose domain is the set of sequences of
octets, and whose range is the set of sequences of
characters from a character repertoire; that is, a
sequence of octets and a character encoding scheme
determines a sequence of characters.
character repertoire
A finite set of characters; e.g. the range of a coded
character set.
code position
An integer. A coded character set and a code position
from its domain determine a character.
coded character set
A function whose domain is a subset of the integers and
whose range is a character repertoire. That is, for some
set of integers (usually of the form {0, 1, 2, ..., N}
), a coded character set and an integer in that set
determine a character. Conversely, a character and a
coded character set determine the character's code
position (or, in rare cases, a few code positions).
conforming HTML user
agent
A user agent that conforms to this specification in its
processing of the Internet Media Type `text/html'.
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RFC 1866 Hypertext Markup Language - 2.0 November 1995
data character
Characters other than markup, which make up the content
of elements.
document character set
a coded character set whose range includes all
characters used in a document. Every SGML document has
exactly one document character set. Numeric character
references are resolved via the document character set.
DTD
document type definition. Rules that apply SGML to the
markup of documents of a particular type, including a
set of element and entity declarations. [SGML]
element
A component of the hierarchical structure defined by a
document type definition; it is identified in a document
instance by descriptive markup, usually a start-tag and
end-tag. [SGML]
end-tag
Descriptive markup that identifies the end of an
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