Frankly, I wouldn’t worry about it. We see tables, we see CSS, and we have to handle both. So we try to score them, you know, well no matter what kind of layout mechanism you use.
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, you know, Web 1.0 kind of connotation to them. But if you have the best site, we will try to find it and we’ll try to rank it highly regardless of whether it’s table-based or CSS-based.
by Matt Cutts - Google's Head of Search Quality Team