HTML and CSS Reference
In-Depth Information
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
With this statement, you declare that your document's root element
is
html
, as defined in the DTD whose public identifier is defined as
"-
//W3C//DTD XHTML 1.0 Strict//EN"
. The browser may know how to find
the DTD matching this public identifier. If it does not, it can use the URL
following the public identifier as an alternative location for the DTD.
As you may have noticed, the preceding
<!DOCTYPE>
directive told the
browser to use the strict XHTML DTD. Here's the one you'll probably use
for your transitional XHTML documents:
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
And, as you might expect, the
<!DOCTYPE>
directive for the frame-based
XHTML DTD is:
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
16.2.2. Understanding Namespaces
As described in the last chapter, an XML DTD defines any number of ele-
ment and attribute names as part of the markup language. These ele-
ments and attributes are stored in a
namespace
that is unique to the
DTD. As you reference elements and attributes in your document, the
