Combining the strength of HTML with the flexibility of XML, Extensible Markup Language sets you free to create the kinds of Web pages you've always imagined. And the best thing is, it's really easy to get the hang of XHTML. If you can give directions to the post office, you can design and build a Web page with XHTML. But here's the catch: While XHTML isn't hard to learn, it does pack a welter of details that you have to wrestle into submission while...