When it comes to building sites some people are still using tables to create their layouts. While these still may work they are outdated and can look unprofessional. This is where CSS and Divs come in. Not only are they the new and latest design technique but they also can give your site a superior look. Some other benefits to using CSS and Divs include faster load times, cross-browser compatibility, lower hosting costs, less time spent, consistency maintained, easier for SEO, etc.
As an expert in CSS and XHTML, I am sometimes irked by having to work with or modify sites that have been coded in years past by developers other than myself. More often than not, they do not adhere to the acceptable web standards that make editing others code much easier. There are a few simple things you can do to make your XHTML much more digestible, and even more search engine friendly!