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Versions and Semantics
The latest HTML standard is Version 4.01, but most updates and
changes to the language standard were made in Version 4.0. Therefore,
throughout the book, we generally refer to the HTML standard as HTML
4, encompassing Versions 4.0 and later. We explicitly state the
"dot" version number only when it
is relevant.
The XHTML standard is currently in its first iteration, 1.0. A second
version (XHTML 1.1) has been proposed but not yet established. For
the most part, XHTML 1.0 is identical to HTML 4.01; we detail their
differences in Chapter 16. Throughout the book, we
specifically note cases where XHTML handles a feature or element
differently than the original language, HTML.
The HTML and XHTML standards make very clear the distinction between
"element types" of a document and
the markup "tags" that delimit
those elements. For example, the standard refers to the paragraph
element type, which is not the same as the
<p> tag. The paragraph element consists of
the accepted element-type name within the starting tag
(<p>), intervening content, and the ending
paragraph tag (</p>). The
<p> tag is the starting tag for the
paragraph element, and its contents, known as attributes, ultimately
affect the paragraph element type's contents.
Although these are important distinctions, we're
pragmatists. It is the markup tag that authors apply in their
documents and that affects any intervening content. Accordingly,
throughout the book, we relax the distinction between element types
and tags, often talking about tags and all related contents and not
necessarily using the term
"element-type" when it would be
technically appropriate to make the distinction. Forgive us the
transgression, but we do so for the sake of clarity.
