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RFC 1866


Hypertext Markup Language - 2.0

Part 2 of 3, p. 20 to 49
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5. Document Structure

   An HTML document is a tree of elements, including a head and body,
   headings, paragraphs, lists, etc. Form elements are discussed in 8,

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5.1. Document Element: HTML

   The HTML document element consists of a head and a body, much like a
   memo or a mail message. The head contains the title and optional
   elements. The body is a text flow consisting of paragraphs, lists,
   and other elements.

5.2. Head: HEAD

   The head of an HTML document is an unordered collection of
   information about the document. For example:

    <TITLE>Introduction to HTML</TITLE>

5.2.1. Title: TITLE

   Every HTML document must contain a <TITLE> element.

   The title should identify the contents of the document in a global
   context. A short title, such as "Introduction" may be meaningless out
   of context. A title such as "Introduction to HTML Elements" is more

      NOTE - The length of a title is not limited; however, long titles
      may be truncated in some applications. To minimize this
      possibility, titles should be fewer than 64 characters.

   A user agent may display the title of a document in a history list or
   as a label for the window displaying the document. This differs from
   headings (5.4, "Headings: H1 ... H6"), which are typically displayed
   within the body text flow.

5.2.2. Base Address: BASE

   The optional <BASE> element provides a base address for interpreting
   relative URLs when the document is read out of context (see 7,
   "Hyperlinks"). The value of the HREF attribute must be an absolute

5.2.3. Keyword Index: ISINDEX

   The <ISINDEX> element indicates that the user agent should allow the
   user to search an index by giving keywords. See 7.5, "Queries and
   Indexes" for details.

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5.2.4. Link: LINK

   The <LINK> element represents a hyperlink (see 7, "Hyperlinks").  Any
   number of LINK elements may occur in the <HEAD> element of an HTML
   document. It has the same attributes as the <A> element (see 5.7.3,
   "Anchor: A").

   The <LINK> element is typically used to indicate authorship, related
   indexes and glossaries, older or more recent versions, document
   hierarchy, associated resources such as style sheets, etc.

5.2.5. Associated Meta-information: META

   The <META> element is an extensible container for use in identifying
   specialized document meta-information.  Meta-information has two main

        * to provide a means to discover that the data set exists
        and how it might be obtained or accessed; and

        * to document the content, quality, and features of a data
        set, indicating its fitness for use.

   Each <META> element specifies a name/value pair. If multiple META
   elements are provided with the same name, their combined contents--
   concatenated as a comma-separated list--is the value associated with
   that name.

        NOTE - The <META> element should not be used where a
        specific element, such as <TITLE>, would be more
        appropriate. Rather than a <META> element with a URI as
        the value of the CONTENT attribute, use a <LINK>

   HTTP servers may read the content of the document <HEAD> to generate
   header fields corresponding to any elements defining a value for the
   attribute HTTP-EQUIV.

        NOTE - The method by which the server extracts document
        meta-information is unspecified and not mandatory. The
        <META> element only provides an extensible mechanism for
        identifying and embedding document meta-information --
        how it may be used is up to the individual server
        implementation and the HTML user agent.

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    Attributes of the META element:

            binds the element to an HTTP header field. An HTTP
            server may use this information to process the document.
            In particular, it may include a header field in the
            responses to requests for this document: the header name
            is taken from the HTTP-EQUIV attribute value, and the
            header value is taken from the value of the CONTENT
            attribute. HTTP header names are not case sensitive.

            specifies the name of the name/value pair. If not
            present, HTTP-EQUIV gives the name.

            specifies the value of the name/value pair.


    If the document contains:

    <META HTTP-EQUIV="Expires"
          CONTENT="Tue, 04 Dec 1993 21:29:02 GMT">
    <meta http-equiv="Keywords" CONTENT="Fred">
    <META HTTP-EQUIV="Reply-to"
          content=" (Roy Fielding)">
    <Meta Http-equiv="Keywords" CONTENT="Barney">

    then the server may include the following header fields:

    Expires: Tue, 04 Dec 1993 21:29:02 GMT
    Keywords: Fred, Barney
    Reply-to: (Roy Fielding)

    as part of the HTTP response to a `GET' or `HEAD' request for
    that document.

    An HTTP server must not use the <META> element to form an HTTP
    response header unless the HTTP-EQUIV attribute is present.

    An HTTP server may disregard any <META> elements that specify
    information controlled by the HTTP server, for example `Server',

    `Date', and `Last-modified'.

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5.2.6. Next Id: NEXTID

   The <NEXTID> element is included for historical reasons only.  HTML
   documents should not contain <NEXTID> elements.

   The <NEXTID> element gives a hint for the name to use for a new <A>
   element when editing an HTML document. It should be distinct from all
   NAME attribute values on <A> elements. For example:

   <NEXTID N=Z27>

5.3. Body: BODY

   The <BODY> element contains the text flow of the document, including
   headings, paragraphs, lists, etc.

   For example:

    <h1>Important Stuff</h1>
    <p>Explanation about important stuff...

5.4. Headings: H1 ... H6

   The six heading elements, <H1> through <H6>, denote section headings.
   Although the order and occurrence of headings is not constrained by
   the HTML DTD, documents should not skip levels (for example, from H1
   to H3), as converting such documents to other representations is
   often problematic.

   Example of use:

    <H1>This is a heading</H1>
    Here is some text
    <H2>Second level heading</H2>
    Here is some more text.

    Typical renderings are:

            Bold, very-large font, centered. One or two blank lines
            above and below.

            Bold, large font, flush-left. One or two blank lines
            above and below.

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            Italic, large font, slightly indented from the left
            margin. One or two blank lines above and below.

            Bold, normal font, indented more than H3. One blank line
            above and below.

            Italic, normal font, indented as H4. One blank line

            Bold, indented same as normal text, more than H5. One
            blank line above.

5.5. Block Structuring Elements

   Block structuring elements include paragraphs, lists, and block
   quotes. They must not contain heading elements, but they may contain
   phrase markup, and in some cases, they may be nested.

5.5.1. Paragraph: P

   The <P> element indicates a paragraph. The exact indentation, leading
   space, etc. of a paragraph is not specified and may be a function of
   other tags, style sheets, etc.

   Typically, paragraphs are surrounded by a vertical space of one line
   or half a line. The first line in a paragraph is indented in some

   Example of use:

    <H1>This Heading Precedes the Paragraph</H1>
    <P>This is the text of the first paragraph.
    <P>This is the text of the second paragraph. Although you do not
    need to start paragraphs on new lines, maintaining this
    convention facilitates document maintenance.</P>
    <P>This is the text of a third paragraph.</P>

5.5.2. Preformatted Text: PRE

   The <PRE> element represents a character cell block of text and is
   suitable for text that has been formatted for a monospaced font.

   The <PRE> tag may be used with the optional WIDTH attribute. The
   WIDTH attribute specifies the maximum number of characters for a line

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   and allows the HTML user agent to select a suitable font and

   Within preformatted text:

        * Line breaks within the text are rendered as a move to the
        beginning of the next line.

            NOTE - References to the "beginning of a new line"
            do not imply that the renderer is forbidden from
            using a constant left indent for rendering
            preformatted text. The left indent may be
            constrained by the width required.

        * Anchor elements and phrase markup may be used.

            NOTE - Constraints on the processing of <PRE>
            content may limit or prevent the ability of the HTML
            user agent to faithfully render phrase markup.

        * Elements that define paragraph formatting (headings,
        address, etc.) must not be used.

            NOTE - Some historical documents contain <P> tags in
            <PRE> elements. User agents are encouraged to treat
            this as a line break. A <P> tag followed by a
            newline character should produce only one line
            break, not a line break plus a blank line.

        * The horizontal tab character (code position 9 in the HTML
        document character set) must be interpreted as the smallest
        positive nonzero number of spaces which will leave the
        number of characters so far on the line as a multiple of 8.
        Documents should not contain tab characters, as they are not
        supported consistently.

    Example of use:

    Line 1.
           Line 2 is to the right of line 1.     <a href="abc">abc</a>
           Line 3 aligns with line 2.            <a href="def">def</a>

Top      Up      ToC       Page 27 Example and Listing: XMP, LISTING

   The <XMP> and <LISTING> elements are similar to the <PRE> element,
   but they have a different syntax. Their content is declared as CDATA,
   which means that no markup except the end-tag open delimiter-in-
   context is recognized (see 9.6 "Delimiter Recognition" of [SGML]).

      NOTE - In a previous draft of the HTML specification, the syntax
      of <XMP> and <LISTING> elements allowed closing tags to be treated
      as data characters, as long as the tag name was not <XMP> or
      <LISTING>, respectively.

   Since CDATA declared content has a number of unfortunate interactions
   with processing techniques and tends to be used and implemented
   inconsistently, HTML documents should not contain <XMP> nor <LISTING>
   elements -- the <PRE> tag is more expressive and more consistently

   The <LISTING> element should be rendered so that at least 132
   characters fit on a line. The <XMP> element should be rendered so
   that at least 80 characters fit on a line but is otherwise identical
   to the <LISTING> element.

      NOTE - In a previous draft, HTML included a <PLAINTEXT> element
      that is similar to the <LISTING> element, except that there is no
      closing tag: all characters after the <PLAINTEXT> start-tag are

5.5.3. Address: ADDRESS

   The <ADDRESS> element contains such information as address, signature
   and authorship, often at the beginning or end of the body of a

   Typically, the <ADDRESS> element is rendered in an italic typeface
   and may be indented.

   Example of use:

    Newsletter editor<BR>
    J.R. Brown<BR>
    JimquickPost News, Jimquick, CT 01234<BR>
    Tel (123) 456 7890

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5.5.4. Block Quote: BLOCKQUOTE

   The <BLOCKQUOTE> element contains text quoted from another source.

   A typical rendering might be a slight extra left and right indent,
   and/or italic font. The <BLOCKQUOTE> typically provides space above
   and below the quote.

   Single-font rendition may reflect the quotation style of Internet
   mail by putting a vertical line of graphic characters, such as the
   greater than symbol (>), in the left margin.

   Example of use:

    I think the play ends
    <P>Soft you now, the fair Ophelia. Nymph, in thy orisons, be all
    my sins remembered.
    but I am not sure.

5.6. List Elements

   HTML includes a number of list elements. They may be used in
   combination; for example, a <OL> may be nested in an <LI> element of
   a <UL>.

   The COMPACT attribute suggests that a compact rendering be used.

5.6.1. Unordered List: UL, LI

   The <UL> represents a list of items -- typically rendered as a
   bulleted list.

   The content of a <UL> element is a sequence of <LI> elements.  For

    <LI>First list item
    <LI>Second list item
     <p>second paragraph of second item
    <LI>Third list item

5.6.2. Ordered List: OL

   The <OL> element represents an ordered list of items, sorted by
   sequence or order of importance. It is typically rendered as a

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   numbered list.

   The content of a <OL> element is a sequence of <LI> elements.  For

    <LI>Click the Web button to open URI window.
    <LI>Enter the URI number in the text field of the Open URI
    window. The Web document you specified is displayed.
       <li>substep 1
       <li>substep 2
    <LI>Click highlighted text to move from one link to another.

5.6.3. Directory List: DIR

   The <DIR> element is similar to the <UL> element. It represents a
   list of short items, typically up to 20 characters each. Items in a
   directory list may be arranged in columns, typically 24 characters

   The content of a <DIR> element is a sequence of <LI> elements.
   Nested block elements are not allowed in the content of <DIR>
   elements. For example:


5.6.4. Menu List: MENU

   The <MENU> element is a list of items with typically one line per
   item. The menu list style is typically more compact than the style of
   an unordered list.

   The content of a <MENU> element is a sequence of <LI> elements.
   Nested block elements are not allowed in the content of <MENU>
   elements. For example:

    <LI>First item in the list.
    <LI>Second item in the list.
    <LI>Third item in the list.

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5.6.5. Definition List: DL, DT, DD

   A definition list is a list of terms and corresponding definitions.
   Definition lists are typically formatted with the term flush-left and
   the definition, formatted paragraph style, indented after the term.

   The content of a <DL> element is a sequence of <DT> elements and/or
   <DD> elements, usually in pairs. Multiple <DT> may be paired with a
   single <DD> element. Documents should not contain multiple
   consecutive <DD> elements.

   Example of use:

    <DT>Term<DD>This is the definition of the first term.
    <DT>Term<DD>This is the definition of the second term.

   If the DT term does not fit in the DT column (typically one third of
   the display area), it may be extended across the page with the DD
   section moved to the next line, or it may be wrapped onto successive
   lines of the left hand column.

   The optional COMPACT attribute suggests that a compact rendering be
   used, because the list items are small and/or the entire list is

   Unless the COMPACT attribute is present, an HTML user agent may leave
   white space between successive DT, DD pairs. The COMPACT attribute
   may also reduce the width of the left-hand (DT) column.

    <DT>Term<DD>This is the first definition in compact format.
    <DT>Term<DD>This is the second definition in compact format.

5.7. Phrase Markup

   Phrases may be marked up according to idiomatic usage, typographic
   appearance, or for use as hyperlink anchors.

   User agents must render highlighted phrases distinctly from plain
   text. Additionally, <EM> content must be rendered as distinct from
   <STRONG> content, and <B> content must rendered as distinct from <I>

   Phrase elements may be nested within the content of other phrase
   elements; however, HTML user agents may render nested phrase elements

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   indistinctly from non-nested elements:

   plain <B>bold <I>italic</I></B> may be rendered
   the same as plain <B>bold </B><I>italic</I>

5.7.1. Idiomatic Elements

   Phrases may be marked up to indicate certain idioms.

      NOTE - User agents may support the <DFN> element, not included in
      this specification, as it has been deployed to some extent. It is
      used to indicate the defining instance of a term, and it is
      typically rendered in italic or bold italic. Citation: CITE

      The <CITE> element is used to indicate the title of a book or
      other citation. It is typically rendered as italics. For example:

      He just couldn't get enough of <cite>The Grapes of Wrath</cite>. Code: CODE

      The <CODE> element indicates an example of code, typically
      rendered in a mono-spaced font. The <CODE> element is intended for
      short words or phrases of code; the <PRE> block structuring
      element (5.5.2, "Preformatted Text: PRE") is more appropriate
       for multiple-line listings. For example:

      The expression <code>x += 1</code>
      is short for <code>x = x + 1</code>. Emphasis: EM

      The <EM> element indicates an emphasized phrase, typically
      rendered as italics. For example:

      A singular subject <em>always</em> takes a singular verb. Keyboard: KBD

      The <KBD> element indicates text typed by a user, typically
      rendered in a mono-spaced font. This is commonly used in
      instruction manuals. For example:

      Enter <kbd>FIND IT</kbd> to search the database.

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      The <SAMP> element indicates a sequence of literal characters,
      typically rendered in a mono-spaced font. For example:

      The only word containing the letters <samp>mt</samp> is dreamt. Strong Emphasis: STRONG

      The <STRONG> element indicates strong emphasis, typically rendered
      in bold. For example:

      <strong>STOP</strong>, or I'll say "<strong>STOP</strong>" again! Variable: VAR

      The <VAR> element indicates a placeholder variable, typically
      rendered as italic. For example:

      Type <SAMP>html-check <VAR>file</VAR> | more</SAMP>
      to check <VAR>file</VAR> for markup errors.

5.7.2. Typographic Elements

      Typographic elements are used to specify the format of marked

      Typical renderings for idiomatic elements may vary between user
      agents. If a specific rendering is necessary -- for example, when
      referring to a specific text attribute as in "The italic parts are
      mandatory" -- a typographic element can be used to ensure that the
      intended typography is used where possible.

      NOTE - User agents may support some typographic elements not
      included in this specification, as they have been deployed to some
      extent. The <STRIKE> element indicates horizontal line through the
      characters, and the <U> element indicates an underline. Bold: B

   The <B> element indicates bold text. Where bold typography is
   unavailable, an alternative representation may be used. Italic: I

   The <I> element indicates italic text. Where italic typography is
   unavailable, an alternative representation may be used.

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   The <TT> element indicates teletype (monospaced )text. Where a
   teletype font is unavailable, an alternative representation may be

5.7.3. Anchor: A

   The <A> element indicates a hyperlink anchor (see 7, "Hyperlinks").
   At least one of the NAME and HREF attributes should be present.
   Attributes of the <A> element:

            gives the URI of the head anchor of a hyperlink.

            gives the name of the anchor, and makes it available as
            a head of a hyperlink.

            suggests a title for the destination resource --
            advisory only. The TITLE attribute may be used:

                * for display prior to accessing the destination
                resource, for example, as a margin note or on a
                small box while the mouse is over the anchor, or
                while the document is being loaded;

                * for resources that do not include a title, such as
                graphics, plain text and Gopher menus, for use as a
                window title.

            The REL attribute gives the relationship(s) described by
            the hyperlink. The value is a whitespace separated list
            of relationship names. The semantics of link
            relationships are not specified in this document.

            same as the REL attribute, but the semantics of the
            relationship are in the reverse direction. A link from A
            to B with REL="X" expresses the same relationship as a
            link from B to A with REV="X". An anchor may have both
            REL and REV attributes.

            specifies a preferred, more persistent identifier for
            the head anchor of the hyperlink. The syntax and

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            semantics of the URN attribute are not yet specified.

            specifies methods to be used in accessing the
            destination, as a whitespace-separated list of names.
            The set of applicable names is a function of the scheme
            of the URI in the HREF attribute. For similar reasons as
            for the TITLE attribute, it may be useful to include the
            information in advance in the link. For example, the
            HTML user agent may chose a different rendering as a
            function of the methods allowed; for example, something
            that is searchable may get a different icon.

5.8. Line Break: BR

   The <BR> element specifies a line break between words (see 6,
   "Characters, Words, and Paragraphs"). For example:

    <P> Pease porridge hot<BR>
    Pease porridge cold<BR>
    Pease porridge in the pot<BR>
    Nine days old.

5.9. Horizontal Rule: HR

   The <HR> element is a divider between sections of text; typically a
   full width horizontal rule or equivalent graphic.  For example:

    <ADDRESS>February 8, 1995, CERN</ADDRESS>

5.10. Image: IMG

   The <IMG> element refers to an image or icon via a hyperlink (see
   7.3, "Simultaneous Presentation of Image Resources").

   HTML user agents may process the value of the ALT attribute as an
   alternative to processing the image resource indicated by the SRC

      NOTE - Some HTML user agents can process graphics linked via
      anchors, but not <IMG> graphics. If a graphic is essential, it
      should be referenced from an <A> element rather than an <IMG>
      element. If the graphic is not essential, then the <IMG> element
      is appropriate.

   Attributes of the <IMG> element:

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            alignment of the image with respect to the text

                * `TOP' specifies that the top of the image aligns
                with the tallest item on the line containing the

                * `MIDDLE' specifies that the center of the image
                aligns with the baseline of the line containing the

                * `BOTTOM' specifies that the bottom of the image
                aligns with the baseline of the line containing the

            text to use in place of the referenced image resource,
            for example due to processing constraints or user

            indicates an image map (see 7.6, "Image Maps").

            specifies the URI of the image resource.

                NOTE - In practice, the media types of image
                resources are limited to a few raster graphic
                formats: typically `image/gif', `image/jpeg'. In
                particular, `text/html' resources are not
                intended to be used as image resources.

    Examples of use:

    <IMG SRC="triangle.xbm" ALT="Warning:"> Be sure
    to read these instructions.

    <a href="http://machine/htbin/imagemap/sample">
    <IMG SRC="sample.xbm" ISMAP>

6. Characters, Words, and Paragraphs

   An HTML user agent should present the body of an HTML document as a
   collection of typeset paragraphs and preformatted text.  Except for
   preformatted elements (<PRE>, <XMP>, <LISTING>, <TEXTAREA>), each
   block structuring element is regarded as a paragraph by taking the

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   data characters in its content and the content of its descendant
   elements, concatenating them, and splitting the result into words,
   separated by space, tab, or record end characters (and perhaps hyphen
   characters). The sequence of words is typeset as a paragraph by
   breaking it into lines.

6.1. The HTML Document Character Set

   The document character set specified in 9.5, "SGML Declaration for
   HTML" must be supported by HTML user agents. It includes the graphic
   characters of Latin Alphabet No. 1, or simply Latin-1.  Latin-1
   comprises 191 graphic characters, including the alphabets of most
   Western European languages.

      NOTE - Use of the non-breaking space and soft hyphen indicator
      characters is discouraged because support for them is not widely

      NOTE - To support non-western writing systems, a larger character
      repertoire will be specified in a future version of HTML. The
      document character set will be [ISO-10646], or some subset that
      agrees with [ISO-10646]; in particular, all numeric character
      references must use code positions assigned by [ISO-10646].

   In SGML applications, the use of control characters is limited in
   order to maximize the chance of successful interchange over
   heterogeneous networks and operating systems. In the HTML document
   character set only three control characters are allowed: Horizontal
   Tab, Carriage Return, and Line Feed (code positions 9, 13, and 10).

   The HTML DTD references the Added Latin 1 entity set, to allow
   mnemonic representation of selected Latin 1 characters using only the
   widely supported ASCII character repertoire. For example:

   Kurt G&ouml;del was a famous logician and mathematician.

   See 9.7.2, "ISO Latin 1 Character Entity Set" for a table of the
   "Added Latin 1" entities, and 13, "The HTML Coded Character Set" for
   a table of the code positions of [ISO 8859-1] and the control
   characters in the HTML document character set.

7. Hyperlinks

   In addition to general purpose elements such as paragraphs and lists,
   HTML documents can express hyperlinks. An HTML user agent allows the
   user to navigate these hyperlinks.

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   A hyperlink is a relationship between two anchors, called the head
   and the tail of the hyperlink[DEXTER]. Anchors are identified by an
   anchor address: an absolute Uniform Resource Identifier (URI),
   optionally followed by a '#' and a sequence of characters called a
   fragment identifier. For example:

   In an anchor address, the URI refers to a resource; it may be used in
   a variety of information retrieval protocols to obtain an entity that
   represents the resource, such as an HTML document. The fragment
   identifier, if present, refers to some view on, or portion of the

   Each of the following markup constructs indicates the tail anchor of
   a hyperlink or set of hyperlinks:

        * <A> elements with HREF present.

        * <LINK> elements.

        * <IMG> elements.

        * <INPUT> elements with the SRC attribute present.

        * <ISINDEX> elements.

        * <FORM> elements with `METHOD=GET'.

   These markup constructs refer to head anchors by a URI, either
   absolute or relative, or a fragment identifier, or both.

   In the case of a relative URI, the absolute URI in the address of the
   head anchor is the result of combining the relative URI with a base
   absolute URI as in [RELURL]. The base document is taken from the
   document's <BASE> element, if present; else, it is determined as in

7.1. Accessing Resources

   Once the address of the head anchor is determined, the user agent may
   obtain a representation of the resource.

   For example, if the base URI is `http://host/x/y.html' and the
   document contains:

   <img src="../icons/abc.gif">

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   then the user agent uses the URI `http://host/icons/abc.gif' to
   access the resource, as in [URL]..

7.2. Activation of Hyperlinks

   An HTML user agent allows the user to navigate the content of the
   document and request activation of hyperlinks denoted by <A>
   elements. HTML user agents should also allow activation of <LINK>
   element hyperlinks.

   To activate a link, the user agent obtains a representation of the
   resource identified in the address of the head anchor. If the
   representation is another HTML document, navigation may begin again
   with this new document.

7.3. Simultaneous Presentation of Image Resources

   An HTML user agent may activate hyperlinks indicated by <IMG> and
   <INPUT> elements concurrently with processing the document; that is,
   image hyperlinks may be processed without explicit request by the
   user. Image resources should be embedded in the presentation at the
   point of the tail anchor, that is the <IMG> or <INPUT> element.

   <LINK> hyperlinks may also be processed without explicit user
   request; for example, style sheet resources may be processed before
   or during the processing of the document.

7.4. Fragment Identifiers

   Any characters following a `#' character in a hypertext address
   constitute a fragment identifier. In particular, an address of the
   form `#fragment' refers to an anchor in the same document.

   The meaning of fragment identifiers depends on the media type of the
   representation of the anchor's resource. For `text/html'
   representations, it refers to the <A> element with a NAME attribute
   whose value is the same as the fragment identifier.  The matching is
   case sensitive. The document should have exactly one such element.
   The user agent should indicate the anchor element, for example by
   scrolling to and/or highlighting the phrase.

   For example, if the base URI is `http://host/x/y.html' and the user
   activated the link denoted by the following markup:

   <p> See: <a href="app1.html#bananas">appendix 1</a>
   for more detail on bananas.

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   Then the user agent accesses the resource identified by
   `http://host/x/app1.html'. Assuming the resource is represented using
   the `text/html' media type, the user agent must locate the <A>
   element whose NAME attribute is `bananas' and begin navigation there.

7.5. Queries and Indexes

   The <ISINDEX> element represents a set of hyperlinks. The user can
   choose from the set by providing keywords to the user agent.  The
   user agent computes the head URI by appending `?' and the keywords to
   the base URI. The keywords are escaped according to [URL] and joined
   by `+'. For example, if a document contains:

    <BASE HREF="http://host/index">

    and the user provides the keywords `apple' and `berry', then the
    user agent must access the resource

    <FORM> elements with `METHOD=GET' also represent sets of
    hyperlinks. See 8.2.2, "Query Forms: METHOD=GET" for details.

7.6. Image Maps

   If the ISMAP attribute is present on an <IMG> element, the <IMG>
   element must be contained in an <A> element with an HREF present.
   This construct represents a set of hyperlinks. The user can choose
   from the set by choosing a pixel of the image. The user agent
   computes the head URI by appending `?' and the x and y coordinates of
   the pixel to the URI given in the <A> element.  For example, if a
   document contains:

   <head><title>ImageMap Example</title>
   <BASE HREF="http://host/index"></head>
   <p> Choose any of these icons:<br>
   <a href="/cgi-bin/imagemap"><img ismap src="icons.gif"></a>

   and the user chooses the upper-leftmost pixel, the chosen
   hyperlink is the one with the URI

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8. Forms

   A form is a template for a form data set and an associated
   method and action URI. A form data set is a sequence of
   name/value pair fields. The names are specified on the NAME
   attributes of form input elements, and the values are given
   initial values by various forms of markup and edited by the
   user. The resulting form data set is used to access an
   information service as a function of the action and method.

   Forms elements can be mixed in with document structuring
   elements. For example, a <PRE> element may contain a <FORM>
   element, or a <FORM> element may contain lists which contain
   <INPUT> elements. This gives considerable flexibility in
   designing the layout of forms.

   Form processing is a level 2 feature.

8.1. Form Elements

8.1.1. Form: FORM

   The <FORM> element contains a sequence of input elements, along
   with document structuring elements. The attributes are:

            specifies the action URI for the form. The action URI of
            a form defaults to the base URI of the document (see 7,

            selects a method of accessing the action URI. The set of
            applicable methods is a function of the scheme of the
            action URI of the form. See 8.2.2, "Query Forms:
            METHOD=GET" and 8.2.3, "Forms with Side-Effects:

            specifies the media type used to encode the name/value
            pairs for transport, in case the protocol does not
            itself impose a format. See 8.2.1, "The form-urlencoded
            Media Type".

8.1.2. Input Field: INPUT

   The <INPUT> element represents a field for user input. The TYPE
   attribute discriminates between several variations of fields.

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   The <INPUT> element has a number of attributes. The set of applicable
   attributes depends on the value of the TYPE attribute. Text Field: INPUT TYPE=TEXT

   The default value of the TYPE attribute is `TEXT', indicating a
   single line text entry field. (Use the <TEXTAREA> element for multi-
   line text fields.)

   Required attributes are:

            name for the form field corresponding to this element.

    The optional attributes are:

            constrains the number of characters that can be entered
            into a text input field. If the value of MAXLENGTH is
            greater the the value of the SIZE attribute, the field
            should scroll appropriately. The default number of
            characters is unlimited.

            specifies the amount of display space allocated to this
            input field according to its type. The default depends
            on the user agent.

            The initial value of the field.

    For example:

<p>Street Address: <input name=street><br>
Postal City code: <input name=city size=16 maxlength=16><br>
Zip Code: <input name=zip size=10 maxlength=10 value="99999-9999"><br> Password Field: INPUT TYPE=PASSWORD

   An <INPUT> element with `TYPE=PASSWORD' is a text field as above,
   except that the value is obscured as it is entered. (see also: 10,
   "Security Considerations").

   For example:

<p>Name: <input name=login> Password: <input type=password name=passwd>

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   An <INPUT> element with `TYPE=CHECKBOX' represents a boolean choice.
   A set of such elements with the same name represents an n-of-many
   choice field. Required attributes are:

            symbolic name for the form field corresponding to this
            element or group of elements.

            The portion of the value of the field contributed by
            this element.

    Optional attributes are:

            indicates that the initial state is on.

    For example:

  <p>What flavors do you like?
  <input type=checkbox name=flavor value=vanilla>Vanilla<br>
  <input type=checkbox name=flavor value=strawberry>Strawberry<br>
  <input type=checkbox name=flavor value=chocolate checked>Chocolate<br> Radio Button: INPUT TYPE=RADIO

   An <INPUT> element with `TYPE=RADIO' represents a boolean choice. A
   set of such elements with the same name represents a 1-of-many choice
   field. The NAME and VALUE attributes are required as for check boxes.
   Optional attributes are:

            indicates that the initial state is on.
   At all times, exactly one of the radio buttons in a set is checked.
   If none of the <INPUT> elements of a set of radio buttons specifies
   `CHECKED', then the user agent must check the first radio button of
   the set initially.

   For example:

    <p>Which is your favorite?
    <input type=radio name=flavor value=vanilla>Vanilla<br>
    <input type=radio name=flavor value=strawberry>Strawberry<br>
    <input type=radio name=flavor value=chocolate>Chocolate<br>

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   An <INPUT> element with `TYPE=IMAGE' specifies an image resource to
   display, and allows input of two form fields: the x and y coordinate
   of a pixel chosen from the image. The names of the fields are the
   name of the field with `.x' and `.y' appended.  `TYPE=IMAGE' implies
   `TYPE=SUBMIT' processing; that is, when a pixel is chosen, the form
   as a whole is submitted.

   The NAME attribute is required as for other input fields. The SRC
   attribute is required and the ALIGN is optional as for the <IMG>
   element (see 5.10, "Image: IMG").

   For example:

    <p>Choose a point on the map:
    <input type=image name=point src="map.gif"> Hidden Field: INPUT TYPE=HIDDEN

   An <INPUT> element with `TYPE=HIDDEN' represents a hidden field.The
   user does not interact with this field; instead, the VALUE attribute
   specifies the value of the field. The NAME and VALUE attributes are

   For example:

   <input type=hidden name=context value="l2k3j4l2k3j4l2k3j4lk23"> Submit Button: INPUT TYPE=SUBMIT

   An <INPUT> element with `TYPE=SUBMIT' represents an input option,
   typically a button, that instructs the user agent to submit the form.
   Optional attributes are:

            indicates that this element contributes a form field
            whose value is given by the VALUE attribute. If the NAME
            attribute is not present, this element does not
            contribute a form field.

            indicates a label for the input (button).

    You may submit this request internally:
    <input type=submit name=recipient value=internal><br>
    or to the external world:
    <input type=submit name=recipient value=world>

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   An <INPUT> element with `TYPE=RESET' represents an input option,
   typically a button, that instructs the user agent to reset the form's
   fields to their initial states. The VALUE attribute, if present,
   indicates a label for the input (button).

   When you are finished, you may submit this request:
   <input type=submit><br>
   You may clear the form and start over at any time: <input type=reset>

8.1.3. Selection: SELECT

   The <SELECT> element constrains the form field to an enumerated list
   of values. The values are given in <OPTION> elements.  Attributes

            indicates that more than one option may be included in
            the value.

            specifies the name of the form field.

            specifies the number of visible items. Select fields of
            size one are typically pop-down menus, whereas select
            fields with size greater than one are typically lists.

    For example:

    <SELECT NAME="flavor">
    <OPTION value="RumRasin">Rum and Raisin
    <OPTION selected>Peach and Orange

   The initial state has the first option selected, unless a SELECTED
   attribute is present on any of the <OPTION> elements. Option: OPTION

   The Option element can only occur within a Select element. It
   represents one choice, and has the following attributes:

            Indicates that this option is initially selected.

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            indicates the value to be returned if this option is
            chosen. The field value defaults to the content of the
            <OPTION> element.

   The content of the <OPTION> element is presented to the user to
   represent the option. It is used as a returned value if the VALUE
   attribute is not present.

8.1.4. Text Area: TEXTAREA

   The <TEXTAREA> element represents a multi-line text field.
   Attributes are:

            the number of visible columns to display for the text
            area, in characters.

            Specifies the name of the form field.

            The number of visible rows to display for the text area,
            in characters.

    For example:

    <TEXTAREA NAME="address" ROWS=6 COLS=64>
    HaL Computer Systems
    1315 Dell Avenue
    Campbell, California 95008

   The content of the <TEXTAREA> element is the field's initial value.

   Typically, the ROWS and COLS attributes determine the visible
   dimension of the field in characters. The field is typically rendered
   in a fixed-width font. HTML user agents should allow text to extend
   beyond these limits by scrolling as needed.

8.2. Form Submission

   An HTML user agent begins processing a form by presenting the
   document with the fields in their initial state. The user is allowed
   to modify the fields, constrained by the field type etc.  When the
   user indicates that the form should be submitted (using a submit
   button or image input), the form data set is processed according to
   its method, action URI and enctype.

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   When there is only one single-line text input field in a form, the
   user agent should accept Enter in that field as a request to submit
   the form.

8.2.1. The form-urlencoded Media Type

   The default encoding for all forms is `application/x-www-form-
   urlencoded'. A form data set is represented in this media type as

        1. The form field names and values are escaped: space
        characters are replaced by `+', and then reserved characters
        are escaped as per [URL]; that is, non-alphanumeric
        characters are replaced by `%HH', a percent sign and two
        hexadecimal digits representing the ASCII code of the
        character. Line breaks, as in multi-line text field values,
        are represented as CR LF pairs, i.e. `%0D%0A'.

        2. The fields are listed in the order they appear in the
        document with the name separated from the value by `=' and
        the pairs separated from each other by `&'. Fields with null
        values may be omitted. In particular, unselected radio
        buttons and checkboxes should not appear in the encoded
        data, but hidden fields with VALUE attributes present

            NOTE - The URI from a query form submission can be
            used in a normal anchor style hyperlink.
            Unfortunately, the use of the `&' character to
            separate form fields interacts with its use in SGML
            attribute values as an entity reference delimiter.
            For example, the URI `http://host/?x=1&y=2' must be
            written `<a href="http://host/?x=1&#38;y=2"' or `<a

            HTTP server implementors, and in particular, CGI
            implementors are encouraged to support the use of
            `;' in place of `&' to save users the trouble of
            escaping `&' characters this way.

8.2.2. Query Forms: METHOD=GET

   If the processing of a form is idempotent (i.e. it has no lasting
   observable effect on the state of the world), then the form method
   should be `GET'. Many database searches have no visible side-effects
   and make ideal applications of query forms.

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   To process a form whose action URL is an HTTP URL and whose method is
   `GET', the user agent starts with the action URI and appends a `?'
   and the form data set, in `application/x-www-form-urlencoded' format
   as above. The user agent then traverses the link to this URI just as
   if it were an anchor (see 7.2, "Activation of Hyperlinks").

      NOTE - The URL encoding may result in very long URIs, which cause
      some historical HTTP server implementations to exhibit defective
      behavior. As a result, some HTML forms are written using
      `METHOD=POST' even though the form submission has no side-effects.

8.2.3. Forms with Side-Effects: METHOD=POST

   If the service associated with the processing of a form has side
   effects (for example, modification of a database or subscription to a
   service), the method should be `POST'.

   To process a form whose action URL is an HTTP URL and whose method is
   `POST', the user agent conducts an HTTP POST transaction using the
   action URI, and a message body of type `application/x-www-form-
   urlencoded' format as above. The user agent should display the
   response from the HTTP POST interaction just as it would display the
   response from an HTTP GET above.

8.2.4. Example Form Submission: Questionnaire Form

   Consider the following document:

    <title>Sample of HTML Form Submission</title>
    <H1>Sample Questionnaire</H1>
    <P>Please fill out this questionnaire:
    <P>Your name: <INPUT NAME="name" size="48">
    <P>Male <INPUT NAME="gender" TYPE=RADIO VALUE="male">
    <P>Female <INPUT NAME="gender" TYPE=RADIO VALUE="female">
    <P>Number in family: <INPUT NAME="family" TYPE=text>
    <P>Cities in which you maintain a residence:
    <LI>Kent <INPUT NAME="city" TYPE=checkbox VALUE="kent">
    <LI>Miami <INPUT NAME="city" TYPE=checkbox VALUE="miami">
    <LI>Other <TEXTAREA NAME="other" cols=48 rows=4></textarea>
    Nickname: <INPUT NAME="nickname" SIZE="42">
    <P>Thank you for responding to this questionnaire.

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    The initial state of the form data set is:






    Note that the radio input has an initial value, while the
    checkbox has none.

    The user might edit the fields and request that the form be
    submitted. At that point, suppose the values are:

            "John Doe"







   The user agent then conducts an HTTP POST transaction using the URI
   `'. The message body would be (ignore the
   line break):

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(page 49 continued on part 3)

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