The only real advantage of using CSS is the ability to use external style sheets. These will make your code less cluttered and reduce the site’s loading time.
The search engines can read easier a clean code. Instead of scanning heavy html tables they’ll get straight to the text, which is the real search engine food.
A site where the text is placed higher in the HTML code has more chances to rank well in the SERPs than a site where the text is hidden within complicated tables.
Many designers prefer tables because these make design easier and the structure of the site somehow cleaner. But the same effect could be obtained by employing the right CSS techniques.
Due to their faster loading times, CSS sites provide for a better user experience than traditional HTML sites.
Some will probably argue this statement; for example those who browse the blogosphere and stumble upon blogs with real slow times. The problem with these blogs lays not in the CSS code, but in the many widgets they use for different purposes (voting buttons, MyBlogLog widgets, The Good Blogs widgets and so on). There is no SEO boost for quick loads.
Search Engine Oracle does recommend CSS for better SEO results, but this doesn’t mean that we cannot help you rank well with a tables-based website. There are enough other SEO techniques that could help you, so don’t hesitate to contact us for a free website audit.