HTML..XHTML.The.Definitive.Guide..5th.Ed.1002002 [Electronic resources] نسخه متنی

Text Conventions

Throughout the book, we use a constant-width
typeface to highlight any literal element of the HTML/XHTML
standards, tags, and attributes. We always use lowercase letters for
tags.[1] We use italic for filenames and URLs
and to indicate new concepts when they are defined. Elements you need
to supply when creating your own documents, such as tag attributes or
user-defined strings, appear in constant-width
italic in the code.

[1] HTML is case-insensitive with regard to tag and
attribute names, but XHTML is case-sensitive. And some HTML items,
such as source filenames, are case-sensitive, so be careful.

We discuss elements of the language throughout the book, but
you'll find each one covered in depth (some might
say in nauseating detail) in a shorthand, quick-reference definition
box that looks like the one that follows. The first line of the box
contains the element name, followed by a brief description of its
function. Next, we list the various attributes, if any, of the
element: those things that you may or must specify as part of the
element.

We use the following symbols to identify tags and attributes that are
not in the HTML 4.01 or XHTML 1.0 standards but are additions to the
languages:

Netscape extension to the standards
Internet Explorer extension to the standards

The description also includes the ending tag, if any, for the
element, along with a general indication of whether the end tag may
be safely omitted in general use in HTML. For the few tags that
require end tags in XHTML but do not have them in HTML, the language
lets you indicate that by placing a forward slash
(/) before the tag's closing
bracket, as in <br />. In
these cases, the tag may also contain attributes, indicated with an
intervening ellipsis, such as <br
... />.

The "Contains" header names the
rule in the HTML grammar that defines the elements to be placed
within this tag. Similarly, the "Used
in" header lists those rules that allow this tag as
part of their content. These rules are defined in Appendix A.

Finally, HTML and XHTML are fairly intertwined languages. You will
occasionally use elements in different ways depending on context, and
many elements share identical attributes. Wherever possible, we place
a cross-reference in the text that leads you to a related discussion
elsewhere in the book. These cross-references, like the one at the
end of this paragraph, serve as a crude paper model of hypertext
documentation, one that would be replaced with a true hypertext link
should this book be delivered in an electronic format. [Section 3.3.1]

We encourage you to follow these references whenever possible. Often,
we cover an attribute briefly and expect you to jump to the
cross-reference for a more detailed discussion. In other cases,
following the link takes you to alternative uses of the element under
discussion or to style and usage suggestions that relate to the
current element.