SEO Tip #35: Are CSS-based layouts better than tables for SEO?
Matt Cutts: Frankly I wouldn’t worry about it. We see tables, we see CSS, and we have to handle both. We try to score them well no matter what kind of layout mechanism you use.
Frankly I would use what’s best for you. A lot of people these days tend to like CSS because it’s easy to change your site. It’s easy to change the layout. It’s very modular whereas tables sort of have this Web 1.0 kind of connotation to them.
But if you have the best site, we will try to find it and we will try to rank it highly regardless of whether it’s table based or CSS based.