XHTML Requirements
XHTML, the latest revision of HTML, adds another required element to your Web pages: the <!DOCTYPE> tag. This tag appears at the top of the file and identifies the file as an HTML document conforming to the XHTML requirements. If you were to create an XHTML-conforming document, it would look like the following:
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-
transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xml:lang="en" lang="en">
<head>
<title>My XHTML Page</title>
</head>
<body>
<p>This is my first XHTML page.</p>
</body>
</html>The <!DOCTYPE> tag has three variations: Strict, Transitional, and Frameset. You declare which one you are using in the top of the file.
Strict Declare this variation when you are certain that your viewers will be accessing your pages from newer browsers that interpret style sheets correctly. The Strict variation looks like this:
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">Transitional Declare this variation when you are not certain how your viewers will be accessing your pages.
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-
transitional.dtd">Frameset Declare this variation when you are working in frames.
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-
frameset.dtd"><html> tag has some new attributes: xmlns, xml:lang, and lang. In HTML, you only have to include the <html> tag to identify the document as an HTML file, but XHTML requires that you use the xmlns attribute to link your document to the W3C’s definition of XHTML, which continues to evolve. Remember to include the <!DOCTYPE> tag and the full <html> tag (shown in the following sample) in all your Web pages.
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-
transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xml:lang="en" lang="en">Related posts:
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