An HTML document is a tree of elements, including a head and body, headings, paragraphs, lists, etc. Form elements are discussed in section Forms.
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.
The head of an HTML document is an unordered collection of information about the document. For example:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <HEAD> <TITLE>Introduction to HTML</TITLE> </HEAD> ...
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 appropriate. (12)
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 (section Headings: H1 ... H6), which are typically displayed within the body text flow.
The optional BASE element provides a base address for interpreting relative URLs when the document is read out of context (see section Hyperlinks). The value of the HREF attribute must be an absolute URI.
The ISINDEX element indicates that the user agent should allow the user to search an index by giving keywords. See section Queries and Indexes for details.
The LINK element represents a hyperlink (see section Hyperlinks). It has the same attributes as the A element (see section Anchor: A).
The LINK element is typically used to indicate authorship, related indexes and glossaries, older or more recent versions, style sheets, document hierarchy etc.
The META element is an extensible container for use in identifying specialized document meta-information. Meta-information has two main functions:
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. (14)
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. (15)
Attributes of the META element:
Examples
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="fielding@ics.uci.edu (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: fielding@ics.uci.edu (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'.
The NEXTID element is included for historical reasons only. HTML document 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>
The BODY element contains the text flow of the document, including headings, paragraphs, lists, etc.
For example:
<BODY> <h1>Important Stuff</h1> <p>Explanation about important stuff... </BODY>
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:
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.
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 cases.
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>
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 and allows the HTML user agent to select a suitable font and indentation.
Within preformatted text:
Example of use:
<PRE>
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>
</PRE>
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]). (19)
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 supported.
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. (20)
The ADDRESS element contains such information as address, signature and authorship, often at the beginning or end of the body of a document.
Typically, the ADDRESS element is rendered in an italic typeface and may be indented.
Example of use:
<ADDRESS> Newsletter editor<BR> J.R. Brown<BR> JimquickPost News, Jimquick, CT 01234<BR> Tel (123) 456 7890 </ADDRESS>
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 poem ends <BLOCKQUOTE> <P>Soft you now, the fair Ophelia. Nymph, in thy orisons, be all my sins remembered. </BLOCKQUOTE> but I am not sure.
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.
The UL represents a list of items -- typically a bulleted list.
The content of a UL element is a sequence of LI elements. For example:
<UL> <LI>First list item <LI>Second list item <p>second paragraph of second item <LI>Third list item </UL>
The OL element represents an ordered list of items, sorted by sequence or order of importance. It is typically rendered as a numbered list.
The content of a OL element is a sequence of LI elements. For example:
<OL> <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. <ol> <li>substep 1 <li>substep 2 </ol> <LI>Click highlighted text to move from one link to another. </OL>
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 wide.
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:
<DIR> <LI>A-H<LI>I-M <LI>M-R<LI>S-Z </DIR>
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:
<MENU> <LI>First item in the list. <LI>Second item in the list. <LI>Third item in the list. </MENU>
A definition list is a list of terms and corresponding definitions. Definition lists are