"I am left with the feeling that all of the sites I have created are 50% elegance , and 50% nasty kludge ."
This quote from a recent Slashdot  discussion on PHP development resonated with the audience. Indeed, as many would attest, a web site usually starts simple but quickly grows into a complex, convoluted messwhere you are afraid of making a change for fear of breaking something else.
Why should a web site so quickly become a nightmare of unmaintainable code, visual and semantic inconsistencies, and outright errors embarrassingly visible to the whole world? Many reasons could be quoted, from limitations specific to the particular web development platforms (such as PHP, ASP, or Perl) to fundamental drawbacks of the "web site as an application" paradigm.
This book is devoted to one very important way in which the majority of today's web sites are brokenand, of course, to the technology which (if correctly applied) can mend this breakage . The problem I'm speaking about is the lack of a consistently semantic and media-independent representation of web site content; the technology that can help you solve this problem is XML; and the key to applying it in web development is XSLT transformations.
Say what you mean. XML is no panacea. It won't magically make your sites self-maintaining or error-proof. But it will give you a critical advantage: Just as a good programming language allows you to freely express your algorithms, XML makes it possible to actually say what you mean in content markup.
The word content is the key. XML is actually more important for web development than any programming languagesimply because you can have a web site without a dynamic engine of any kind, but there cannot exist a web site without content.
In fact, a lot of the approaches in this book apply not only to web sites but to any XML-based document workflows, such as books or technical documentation. XML stimulates thinking about content as such , abstracting it not only from its presentation but from any processing requirements as well.