9.2. Setting Up an HTML Document
skeletal structure of an HTML document according to the HTML 4.01
specification is as follows:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
Contents of Document...
This document has three components: a document type declaration
(<!DOCTYPE>), the header section
(<head>), and the body of the document
The HTML standard requires that the entire document appear within the
<html> container, but most browsers can
properly display the contents of the document even if these tags are
omitted. All HTML documents are made up of two main structures, the
head (also called the "header")
and the body. The exception to this rule is
when the document contains a frameset
place of the body. For more information about framesets, see Chapter 14, "Frames".
9.2.1. The Document Type Declaration
In order to be valid (i.e., to conform precisely to the HTML
standard), an HTML document needs to begin with a document
type declaration that identifies
the version of HTML that is used in the document. There are three
distinct versions of HTML 4.01 (Strict, Transitional, and Frameset),
each defined by a distinct document type definition (DTD). The DTD
documents live on the W3C server at a stable URL.
The document's DTD is specified at the beginning of the
document using the SGML declaration
<!DOCTYPE> (document type). The remainder of
the declaration contains two methods for pointing to DTD information:
one a publicly recognized document, the other a specific URL in case
the browsing device does not recognize the public identifier.
If you are following the Strict version of HTML 4.01 (the version
that omits all deprecated and browser-specific tags), use this
document type definition:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
If your document includes deprecated tags, point to the Transitional
DTD using this document type definition:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
If your document uses frames, then identify the Frameset DTD. The
Frameset DTD is the same as the Transitional version (it includes
deprecated yet supported tags), with the addition of frame-specific
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN"
DOCTYPE and Standards-Compliant Browsers
Until recently, it was recommended that HTML documents begin with a
declaration, but it wasn't put to much practical use. That has
changed, and now you can use DOCTYPE to make the latest browser
versions live up to their full potential.
Netscape 6, Internet Explorer 6 (Windows), and Internet Explorer 5
(Mac) switch into a strict, standards-compliant mode when they detect
a DOCTYPE specifying the Strict HTML 4.01 DTD. By placing this
declaration at the beginning of your document, you can write your
documents and style sheets according to the standards and have
confidence that they will work the way they should in these latest
browsers. This is a great way to get started using
standards-compliant code right away.
If the DOCTYPE declaration is missing or set to Transitional, these
browsers revert to their legacy behavior of allowing the nonstandard
code, intricate hacks, and common workarounds that are common in
current web authoring practices. This allows new browsers to display
existing documents properly.
9.2.2. The Document Header
The header, delimited by the
<head> tag, contains information that
describes the HTML document. The head tag has no attributes of its
own; it merely serves as a container for other tags that help define
and manage the document's contents.
most commonly used element within the header is the document title
(within <title> tags, as shown in the
example above), which provides a description of the page's
contents. In HTML 4.01, this is a required element, which means that
every HTML document must have a meaningful title in its header. The
title is typically displayed in the top bar of the browser, outside
the regular content window.
Titles should contain only ASCII characters (letters, numbers, and
basic punctuation). Special characters (such as
&) should be referred to by their character
entities within the title, for example:
<TITLE>The Adventures of Peto & Fleck</TITLE>
The title is what's displayed in a user's bookmarks or
"hot list." Search engines rely heavily on document
titles as well. For these reasons, it's important to provide
thoughtful and descriptive titles for all your documents and avoid
vague titles like "Welcome" or "My Page."
18.104.22.168. Other header elements
Other useful HTML elements are also placed within
<head> tags of a document:
This tag establishes the document's base location, which serves
as a reference for all pathnames and links in the document. For more
information, see Chapter 11, "Creating Links".
Deprecated. This tag was once used to add a
simple search function to a page. It has been deprecated by HTML 4.01
in favor of form inputs.
This tag defines the relationship between the current document and
another document. Although it can signify relationships such as
index, next, and previous, it is most often used today to link a
document to an external style sheet (see
Chapter 17, "Cascading Style Sheets").
"Meta" tags are used to provide information about a
document, such as keywords or descriptions to aid search engines. It
may also be used for client-pull functions. The
<meta> tag is discussed later in this
header using this tag.
Embedded style sheets must be added to the document header by placing
the <style> element within the
<head> container. For more information, see
Chapter 17, "Cascading Style Sheets".
9.2.3. The Document Body
The document body,
delimited by <body> tags, contains the
contents of the document -- the part that displays in the browser
The body of an HTML document might consist of just a few paragraphs
of text, a single image, or a complex combination of text, images,
tables, and multimedia objects. What you put on the page is up to
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