XHTML+CSS is the new and best way to create a Web page or site. It allows (no, forces) you to separate your site's content from its presentation. The XHTML contains the site’s content/markup, while the CSS controls the site’s presentation/design. Separating content from presentation offers many benefits, as you’ll see. I’ve seen this type of markup called “semantic markup,” and that’s the description we’ll use often throughout this Web site.
Ease of updating. You could, for example, change the text of dozens of lists on your Web site to all caps by simply adding one line to your Cascading Style Sheet: ul {text-transform: uppercase ;}
Semantic markup is informational. The semantic markup using the header (H1) tags says that this is clearly a heading. The older presentational markup said virtually nothing to anyone reading it. It was not descriptive.
Computers understand semantic markup. Semantic markup describes the content, making it much easier and more meaningful to a computer program (which is helpful now and will become more so in the future.) Example: More accessible code for blind and partially sighted users.
Pages load faster. Pages marked up semantically load more quickly, if only because there is less code. That’s especially true when compared with sites using nested tables.
Consistent-looking pages. Using XHTML+CSS makes it extremely easy to maintain visual consistency throughout a site. Since pages use the same CSS document for their layout, they are all formatted the same.
Improved visibility to search engines. Search engines need to read your pages, so by improving your site’s semantics you are also improving your visibility to the search engines.
Better search engine optimization. Most search engines weigh keyword importance by what they are. By using semantic markup, you are essentially telling the search engine what is important, and what is less important. For example, keywords in the headings (clearly marked with an H1, H2, H3, etc. and easily seen by search engines) are deemed more important than keywords in the paragraphs.
Ready for the future. By writing semantic markup you are future-proofing your XHTML documents -- they will be able to be read by the greatest number of people -- and by computers.