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RFC 1866


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Hypertext Markup Language - 2.0

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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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    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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   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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        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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            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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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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    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
            element. [SGML]

    entity
            data with an associated notation or interpretation; for
            example, a sequence of octets associated with an
            Internet Media Type. [SGML]

    fragment identifier
            the portion of an HREF attribute value following the `#'
            character which modifies the presentation of the
            destination of a hyperlink.

    form data set
            a sequence of name/value pairs; the names are given by
            an HTML document and the values are given by a user.

    HTML document
            An SGML document conforming to this document type
            definition.

    hyperlink
            a relationship between two anchors, called the head and
            the tail. The link goes from the tail to the head. The
            head and tail are also known as destination and source,
            respectively.

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    markup
            Syntactically delimited characters added to the data of
            a document to represent its structure. There are four
            different kinds of markup: descriptive markup (tags),
            references, markup declarations, and processing
            instructions. [SGML]

    may
            A document or user interface is conforming whether this
            statement applies or not.

    media type
            an Internet Media Type, as per [IMEDIA].

    message entity
            a head and body. The head is a collection of name/value
            fields, and the body is a sequence of octets. The head
            defines the content type and content transfer encoding
            of the body. [MIME]

    minimally conforming
    HTML user agent
            A user agent that conforms to this specification except
            for form processing. It may only process level 1 HTML
            documents.

    must
            Documents or user agents in conflict with this statement
            are not conforming.

    numeric character
    reference
            markup that refers to a character by its code position
            in the document character set.

    SGML document
            A sequence of characters organized physically as a set
            of entities and logically into a hierarchy of elements.
            An SGML document consists of data characters and markup;
            the markup describes the structure of the information
            and an instance of that structure. [SGML]

    shall
            If a document or user agent conflicts with this
            statement, it does not conform to this specification.

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    should
            If a document or user agent conflicts with this
            statement, undesirable results may occur in practice
            even though it conforms to this specification.

    start-tag
            Descriptive markup that identifies the start of an
            element and specifies its generic identifier and
            attributes. [SGML]

    syntax-reference
    character set
            A coded character set whose range includes all
            characters used for markup; e.g. name characters and
            delimiter characters.

    tag
            Markup that delimits an element. A tag includes a name
            which refers to an element declaration in the DTD, and
            may include attributes. [SGML]

    text entity
            A finite sequence of characters. A text entity typically
            takes the form of a sequence of octets with some
            associated character encoding scheme, transmitted over
            the network or stored in a file. [SGML]

    typical
            Typical processing is described for many elements. This
            is not a mandatory part of the specification but is
            given as guidance for designers and to help explain the
            uses for which the elements were intended.

    URI
            A Uniform Resource Identifier is a formatted string that
            serves as an identifier for a resource, typically on the
            Internet. URIs are used in HTML to identify the anchors
            of hyperlinks. URIs in common practice include Uniform
            Resource Locators (URLs)[URL] and Relative URLs
            [RELURL].

    user agent
            A component of a distributed system that presents an
            interface and processes requests on behalf of a user;
            for example, a www browser or a mail user agent.

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    WWW
            The World-Wide Web is a hypertext-based, distributed
            information system created by researchers at CERN in
            Switzerland. <URL:http://www.w3.org/>

3. HTML as an Application of SGML

   HTML is an application of ISO 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[SGML]. The public text -- DTD and SGML declaration --
   of the HTML document type definition are provided in 9, "HTML Public
   Text".

   The term "HTML" refers to both the document type defined here and the
   markup language for representing instances of this document type.

3.1. SGML Documents

   An HTML document is an SGML document; that is, a sequence of
   characters organized physically into a set of entities, and logically
   as a hierarchy of elements.

   In the SGML specification, the first production of the SGML syntax
   grammar separates an SGML document into three parts: an SGML
   declaration, a prologue, and an instance. For the purposes of this
   specification, the prologue is a DTD. This DTD describes another
   grammar: the start symbol is given in the doctype declaration, the
   terminals are data characters and tags, and the productions are
   determined by the element declarations. The instance must conform to
   the DTD, that is, it must be in the language defined by this grammar.

   The SGML declaration determines the lexicon of the grammar. It
   specifies the document character set, which determines a character
   repertoire that contains all characters that occur in all text
   entities in the document, and the code positions associated with
   those characters.

   The SGML declaration also specifies the syntax-reference character
   set of the document, and a few other parameters that bind the
   abstract syntax of SGML to a concrete syntax. This concrete syntax
   determines how the sequence of characters of the document is mapped
   to a sequence of terminals in the grammar of the prologue.

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   For example, consider the following document:

    <!DOCTYPE html PUBLIC "-//IETF//DTD HTML 2.0//EN">
    <title>Parsing Example</title>
    <p>Some text. <em>&#42;wow&#42;</em></p>

   An HTML user agent should use the SGML declaration that is given in
   9.5, "SGML Declaration for HTML". According to its document character
   set, `&#42;' refers to an asterisk character, `*'.

   The instance above is regarded as the following sequence of
   terminals:

        1. start-tag: TITLE

        2. data characters: "Parsing Example"

        3. end-tag: TITLE

        4. start-tag: P

        5. data characters "Some text."

        6. start-tag: EM

        7. data characters: "*wow*"

        8. end-tag: EM

        9. end-tag: P

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   The start symbol of the DTD grammar is HTML, and the productions are
   given in the public text identified by `-//IETF//DTD HTML 2.0//EN'
   (9.1, "HTML DTD"). The terminals above parse as:

       HTML
        |
        \-HEAD
        |  |
        |  \-TITLE
        |      |
        |      \-<TITLE>
        |      |
        |      \-"Parsing Example"
        |      |
        |      \-</TITLE>
        |
        \-BODY
          |
          \-P
            |
            \-<P>
            |
            \-"Some text. "
            |
            \-EM
            |  |
            |  \-<EM>
            |  |
            |  \-"*wow*"
            |  |
            |  \-</EM>
            |
            \-</P>

   Some of the elements are delimited explicitly by tags, while the
   boundaries of others are inferred. The <HTML> element contains a
   <HEAD> element and a <BODY> element. The <HEAD> contains <TITLE>,
   which is explicitly delimited by start- and end-tags.

3.2. HTML Lexical Syntax

   SGML specifies an abstract syntax and a reference concrete syntax.
   Aside from certain quantities and capacities (e.g. the limit on the
   length of a name), all HTML documents use the reference concrete
   syntax. In particular, all markup characters are in the repertoire of
   [ISO-646]. Data characters are drawn from the document character set
   (see 6, "Characters, Words, and Paragraphs").

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   A complete discussion of SGML parsing, e.g. the mapping of a sequence
   of characters to a sequence of tags and data, is left to the SGML
   standard[SGML]. This section is only a summary.

3.2.1. Data Characters

   Any sequence of characters that do not constitute markup (see 9.6
   "Delimiter Recognition" of [SGML]) are mapped directly to strings of
   data characters. Some markup also maps to data character strings.
   Numeric character references map to single-character strings, via the
   document character set. Each reference to one of the general entities
   defined in the HTML DTD maps to a single-character string.

   For example,

    abc&lt;def    => "abc","<","def"
    abc&#60;def   => "abc","<","def"

   The terminating semicolon on entity or numeric character references
   is only necessary when the character following the reference would
   otherwise be recognized as part of the name (see 9.4.5 "Reference
   End" in [SGML]).

    abc &lt def     => "abc ","<"," def"
    abc &#60 def    => "abc ","<"," def"

   An ampersand is only recognized as markup when it is followed by a
   letter or a `#' and a digit:

    abc & lt def    => "abc & lt def"
    abc &# 60 def    => "abc &# 60 def"

   A useful technique for translating plain text to HTML is to replace
   each '<', '&', and '>' by an entity reference or numeric character
   reference as follows:

                     ENTITY      NUMERIC
           CHARACTER REFERENCE   CHAR REF     CHARACTER DESCRIPTION
           --------- ----------  -----------  ---------------------
             &       &amp;       &#38;        Ampersand
             <       &lt;        &#60;        Less than
             >       &gt;        &#62;        Greater than

        NOTE - There are SGML mechanisms, CDATA and RCDATA
        declared content, that allow most `<', `>', and `&'
        characters to be entered without the use of entity
        references. Because these mechanisms tend to be used and
        implemented inconsistently, and because they conflict

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        with techniques for reducing HTML to 7 bit ASCII for
        transport, they are deprecated in this version of HTML.
        See 5.5.2.1, "Example and Listing: XMP, LISTING".

3.2.2. Tags

   Tags delimit elements such as headings, paragraphs, lists, character
   highlighting, and links. Most HTML elements are identified in a
   document as a start-tag, which gives the element name and attributes,
   followed by the content, followed by the end tag. Start-tags are
   delimited by `<' and `>'; end tags are delimited by `</' and `>'. An
   example is:

   <H1>This is a Heading</H1>

   Some elements only have a start-tag without an end-tag. For example,
   to create a line break, use the `<BR>' tag.  Additionally, the end
   tags of some other elements, such as Paragraph (`</P>'), List Item
   (`</LI>'), Definition Term (`</DT>'), and Definition Description
   (`</DD>') elements, may be omitted.

   The content of an element is a sequence of data character strings and
   nested elements. Some elements, such as anchors, cannot be nested.
   Anchors and character highlighting may be put inside other
   constructs. See the HTML DTD, 9.1, "HTML DTD" for full details.

      NOTE - The SGML declaration for HTML specifies SHORTTAG YES, which
      means that there are other valid syntaxes for tags, such as NET
      tags, `<EM/.../'; empty start tags, `<>'; and empty end-tags,
      `</>'. Until support for these idioms is widely deployed, their
      use is strongly discouraged.

3.2.3. Names

   A name consists of a letter followed by letters, digits, periods, or
   hyphens. The length of a name is limited to 72 characters by the
   `NAMELEN' parameter in the SGML declaration for HTML, 9.5, "SGML
   Declaration for HTML". Element and attribute names are not case
   sensitive, but entity names are.  For example, `<BLOCKQUOTE>',
   `<BlockQuote>', and `<blockquote>' are equivalent, whereas `&amp;' is
   different from `&AMP;'.

   In a start-tag, the element name must immediately follow the tag open
   delimiter `<'.

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3.2.4. Attributes

   In a start-tag, white space and attributes are allowed between the
   element name and the closing delimiter. An attribute specification
   typically consists of an attribute name, an equal sign, and a value,
   though some attribute specifications may be just a name token. White
   space is allowed around the equal sign.

   The value of the attribute may be either:

        * A string literal, delimited by single quotes or double
        quotes and not containing any occurrences of the delimiting
        character.

            NOTE - Some historical implementations consider any
            occurrence of the `>' character to signal the end of
            a tag. For compatibility with such implementations,
            when `>' appears in an attribute value, it should be
            represented with a numeric character reference. For
            example, `<IMG SRC="eq1.jpg" alt="a>b">' should be
            written `<IMG SRC="eq1.jpg" alt="a&#62;b">' or `<IMG
            SRC="eq1.jpg" alt="a&gt;b">'.

        * A name token (a sequence of letters, digits, periods, or
        hyphens). Name tokens are not case sensitive.

            NOTE - Some historical implementations allow any
            character except space or `>' in a name token.

   In this example, <img> is the element name, src is the attribute
   name, and `http://host/dir/file.gif' is the attribute value:

   <img src='http://host/dir/file.gif'>

   A useful technique for computing an attribute value literal for a
   given string is to replace each quote and white space character by an
   entity reference or numeric character reference as follows:

                     ENTITY      NUMERIC
           CHARACTER REFERENCE   CHAR REF     CHARACTER DESCRIPTION
           --------- ----------  -----------  ---------------------
             HT                  &#9;         Tab
             LF                  &#10;        Line Feed
             CR                  &#13;        Carriage Return
             SP                  &#32;        Space
             "       &quot;      &#34;        Quotation mark
             &       &amp;       &#38;        Ampersand

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   For example:

   <IMG SRC="image.jpg" alt="First &quot;real&quot; example">

   The `NAMELEN' parameter in the SGML declaration (9.5, "SGML
   Declaration for HTML") limits the length of an attribute value to
   1024 characters.

   Attributes such as ISMAP and COMPACT may be written using a minimized
   syntax (see 7.9.1.2 "Omitted Attribute Name" in [SGML]). The markup:

   <UL COMPACT="compact">

   can be written using a minimized syntax:

   <UL COMPACT>

   NOTE - Some historical implementations only understand the minimized
   syntax.

3.2.5. Comments

   To include comments in an HTML document, use a comment declaration. A
   comment declaration consists of `<!' followed by zero or more
   comments followed by `>'. Each comment starts with `--' and includes
   all text up to and including the next occurrence of `--'. In a
   comment declaration, white space is allowed after each comment, but
   not before the first comment.  The entire comment declaration is
   ignored.

      NOTE - Some historical HTML implementations incorrectly consider
      any `>' character to be the termination of a comment.

   For example:

    <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
    <HEAD>
    <TITLE>HTML Comment Example</TITLE>
    <!-- Id: html-sgml.sgm,v 1.5 1995/05/26 21:29:50 connolly Exp  -->
    <!-- another -- -- comment -->
    <!>
    </HEAD>
    <BODY>
    <p> <!- not a comment, just regular old data characters ->

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3.3. HTML Public Text Identifiers

   To identify information as an HTML document conforming to this
   specification, each document must start with one of the following
   document type declarations.

   <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">

   This document type declaration refers to the HTML DTD in 9.1, "HTML
   DTD".

      NOTE - If the body of a `text/html' message entity does not begin
      with a document type declaration, an HTML user agent should infer
      the above document type declaration.

   <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Level 2//EN">

   This document type declaration also refers to the HTML DTD which
   appears in 9.1, "HTML DTD".

   <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Level 1//EN">

   This document type declaration refers to the level 1 HTML DTD in 9.3,
   "Level 1 HTML DTD". Form elements must not occur in level 1
   documents.

   <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Strict//EN">
   <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Strict Level 1//EN">

   These two document type declarations refer to the HTML DTD in 9.2,
   "Strict HTML DTD" and 9.4, "Strict Level 1 HTML DTD". They refer to
   the more structurally rigid definition of HTML.

   HTML user agents may support other document types. In particular,
   they may support other formal public identifiers, or other document
   types altogether. They may support an internal declaration subset
   with supplemental entity, element, and other markup declarations.

3.4. Example HTML Document

    <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
    <HTML>
    <!-- Here's a good place to put a comment. -->
    <HEAD>
    <TITLE>Structural Example</TITLE>
    </HEAD><BODY>
    <H1>First Header</H1>
    <P>This is a paragraph in the example HTML file. Keep in mind

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    that the title does not appear in the document text, but that
    the header (defined by H1) does.</P>
    <OL>
    <LI>First item in an ordered list.
    <LI>Second item in an ordered list.
      <UL COMPACT>
      <LI> Note that lists can be nested;
      <LI> Whitespace may be used to assist in reading the
           HTML source.
      </UL>
    <LI>Third item in an ordered list.
    </OL>
    <P>This is an additional paragraph. Technically, end tags are
    not required for paragraphs, although they are allowed. You can
    include character highlighting in a paragraph. <EM>This sentence
    of the paragraph is emphasized.</EM> Note that the &lt;/P&gt;
    end tag has been omitted.
    <P>
    <IMG SRC ="triangle.xbm" alt="Warning: ">
    Be sure to read these <b>bold instructions</b>.
    </BODY></HTML>

4. HTML as an Internet Media Type

   An HTML user agent allows users to interact with resources which have
   HTML representations. At a minimum, it must allow users to examine
   and navigate the content of HTML level 1 documents. HTML user agents
   should be able to preserve all formatting distinctions represented in
   an HTML document, and be able to simultaneously present resources
   referred to by IMG elements (they may ignore some formatting
   distinctions or IMG resources at the request of the user). Level 2
   HTML user agents should support form entry and submission.

4.1. text/html media type

   This specification defines the Internet Media Type [IMEDIA] (formerly
   referred to as the Content Type [MIME]) called `text/html'. The
   following is to be registered with [IANA].

    Media Type name
            text

    Media subtype name
            html

    Required parameters
            none

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    Optional parameters
            level, charset

    Encoding considerations
            any encoding is allowed

    Security considerations
            see 10, "Security Considerations"

    The optional parameters are defined as follows:

    Level
            The level parameter specifies the feature set used in
            the document. The level is an integer number, implying
            that any features of same or lower level may be present
            in the document. Level 1 is all features defined in this
            specification except those that require the <FORM>
            element. Level 2 includes form processing. Level 2 is
            the default.

    Charset
            The charset parameter (as defined in section 7.1.1 of
            RFC 1521[MIME]) may be given to specify the character
            encoding scheme used to represent the HTML document as a
            sequence of octets. The default value is outside the
            scope of this specification; but for example, the
            default is `US-ASCII' in the context of MIME mail, and
            `ISO-8859-1' in the context of HTTP [HTTP].

4.2. HTML Document Representation

   A message entity with a content type of `text/html' represents an
   HTML document, consisting of a single text entity. The `charset'
   parameter (whether implicit or explicit) identifies a character
   encoding scheme. The text entity consists of the characters
   determined by this character encoding scheme and the octets of the
   body of the message entity.

4.2.1. Undeclared Markup Error Handling

   To facilitate experimentation and interoperability between
   implementations of various versions of HTML, the installed base of
   HTML user agents supports a superset of the HTML 2.0 language by
   reducing it to HTML 2.0: markup in the form of a start-tag or end-
   tag, whose generic identifier is not declared is mapped to nothing
   during tokenization. Undeclared attributes are treated similarly. The
   entire attribute specification of an unknown attribute (i.e., the
   unknown attribute and its value, if any) should be ignored. On the

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   other hand, references to undeclared entities should be treated as
   data characters.

   For example:

    <div class=chapter><h1>foo</h1><p>...</div>
      => <H1>,"foo",</H1>,<P>,"..."
    xxx <P ID=z23> yyy
      => "xxx ",<P>," yyy
    Let &alpha; &amp; &beta; be finite sets.
      => "Let &alpha; & &beta; be finite sets."

   Support for notifying the user of such errors is encouraged.

   Information providers are warned that this convention is not binding:
   unspecified behavior may result, as such markup does not conform to
   this specification.

4.2.2. Conventional Representation of Newlines

   SGML specifies that a text entity is a sequence of records, each
   beginning with a record start character and ending with a record end
   character (code positions 10 and 13 respectively) (section 7.6.1,
   "Record Boundaries" in [SGML]).

   [MIME] specifies that a body of type `text/*' is a sequence of lines,
   each terminated by CRLF, that is, octets 13, 10.

   In practice, HTML documents are frequently represented and
   transmitted using an end of line convention that depends on the
   conventions of the source of the document; frequently, that
   representation consists of CR only, LF only, or a CR LF sequence.
   Hence the decoding of the octets will often result in a text entity
   with some missing record start and record end characters.

   Since there is no ambiguity, HTML user agents are encouraged to infer
   the missing record start and end characters.

   An HTML user agent should treat end of line in any of its variations
   as a word space in all contexts except preformatted text. Within
   preformatted text, an HTML user agent should treat any of the three
   common representations of end-of-line as starting a new line.



(page 20 continued on part 2)

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