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3.7 The Document Header
The
document header describes the various properties of the document,
including its title, position within the Web, and relationship with
other documents. Most of the data contained within the document
header is never actually rendered as content visible to the user.
3.7.1 The <head> Tag
The <head> tag serves to encapsulate other header
tags. Place it at the beginning of your document, just after the
<html> tag and before the
<body> or
<frameset> tag. Both the
<head> tag and its corresponding ending
</head> tag can be unambiguously inferred by
the browser and so can be safely omitted from an HTML, but not an
XHTML, document. We encourage you to include them in all your
documents, since they promote readability and support document
automation.
<head>Function Defines the document header Attributes dirlangprofile End tag </head>; rarely omitted in HTML Contains head_content Used in html_tag |
The <head> tag may contain a number of other
tags that help define and manage the document''s
content. These include, in any order of appearance:
<base>, <isindex>,
<link>, <meta>,
<nextid>, <object>,
<script>, <style>,
and <title>.
3.7.1.1 The dir and lang attributes
As we discussed in the sections about the
<html> tag attributes,
dir
and lang help extend HTML and XHTML to an
international audience. [Section 3.6.1.1] [Section 3.6.1.2]
3.7.1.2 The profile attribute
Often, the header of a document
contains a number of <meta> tags used to
convey additional information about the document to the browser. In
the future, authors may use predefined profiles of standard document
metadata to better describe their documents. The
profile attribute supplies the URL of the profile
associated with the current document.
The format of a profile and how it might be used by a browser are not
yet defined; this attribute is primarily a placeholder for future
development.
3.7.2 The <title> Tag
The <title> tag does exactly what
you might expect: the words you place inside its start and end tags
define the title for your document. (This stuff is pretty much
self-explanatory and easier than you might think at first glance.)
The title is used by the browser in some special manner, most often
placed in the browser window''s title bar or on a
status line. Usually, too, the title becomes the default name for a
link to the document if the document is added to a link collection or
to a user''s favorites or bookmarks list.
<title>Function Defines the document title Attributes dirlang End tag </title>; never omitted Contains plain_text Used in head_content |
The <title> tag is the only thing required
within the <head> tag. Since the
<head> tag itself and even the
<html> tag can safely be omitted, the
<title> tag could be the first line within a
valid HTML document. Beyond that, most browsers will even supply a
generic title for documents lacking a
<title> tag, such as the
document''s filename, so you don''t
even have to supply a title. That goes a bit too far even for our
down-and-dirty tastes, though. No respectable author should serve up
a document missing the <title> tag and a
title.
Browsers do not specially format title text, and they ignore anything
other than text inside the title start and end tags. For instance,
they will ignore any images or links to other documents.
Here''s an even barer barebones example of a valid
HTML document, to highlight the header and title tags; watch what
happens when Netscape displays it in Figure 3-2:
<html>
<head>
<title>HTML and XHTML: The Definitive Guide</title>
</head>
</html>
Figure 3-2. What''s in a <title>?
3.7.2.1 What''s in a title?
Selecting the right title is crucial
to defining a document and ensuring that it can be effectively used
on the Web.
Keep in mind that users can access each of the documents in your
collection in nearly any order and independently of one another. Each
document''s title should therefore define the
document both within the context of your other documents and on its
own merits.
Titles that include references to document sequencing are usually
inappropriate. Simple titles, like "Chapter
2" or "Part VI,"
do little to help a user understand what the document might contain.
More descriptive titles, such as "Chapter 2:
Advanced Square Dancing" or "Part
VI: Churchill''s Youth and
Adulthood," convey both a sense of place within a
larger set of documents and specific content that invites the reader
to read on.
Self-referential titles also aren''t very useful. A
title like "Home Page" is
completely content-free, as are titles like
"Feedback Page" or
"Popular Links." You want a title
to convey a sense of content and purpose so that users can decide,
based upon the title alone, whether to visit that page or not.
"The Kumquat Lover''s Home
Page" is descriptive and likely to draw in lovers of
the bitter fruit, as are "Kumquat
Lover''s Feedback Page" and
"Popular Links Frequented by Kumquat
Lovers."
People spend a great deal of time creating documents for the Web,
often only to squander that effort with an uninviting, ineffective
title. As special software that automatically collects links for
users becomes more prevalent on the Web, the only descriptive phrases
associated with your pages when they are inserted into some vast link
database will be the titles you choose for them. We
can''t emphasize this enough: take care to select
descriptive, useful, context-independent titles for each of your
documents.
3.7.2.2 The dir and lang attributes
The dir
and lang attributes help extend HTML and XHTML to
an international audience. [Section 3.6.1.1] [Section 3.6.1.2]
3.7.3 Related Header Tags
Other tags you may include within the <head>
tag deal with specific aspects of document creation, management,
linking, automation, or layout. That''s why we only
mention them here and describe them in greater detail in other, more
appropriate sections and chapters of this book. Briefly, the special
header tags are:
<base> and <link>
Define the current document''s base location and
relationship to other documents. [<base>] [<link>]
<isindex>
Deprecated in HTML 4, the
<isindex> tag at one time could be used to
create automatic document indexing forms, allowing users to search
databases of information using the current document as a querying
tool. [<isindex>]
<nextid>
Not supported in HTML 4 or XHTML, the
<nextid> tag tried to make creation of
unique labels easier when using document automation tools. [<nextid>]
<meta>
Provides additional document data not
supplied by any of the other <head> tags.
[<meta>]
<object>
Defines methods by which nonstandard
objects can be rendered by the browser. [Section 12.2.1]
<script>
Defines one or more scripts that can be
invoked by elements within the document. [Section 12.3.1]
<style>
Lets you create CSS properties to control
body-content display characteristics for the entire document. [<style>]
