jtracking is right of course, there is more to
SEO than just validating and using tableless design, however, there is no reason not to get a good start.
Using Dreamweaver itself, if done properly (hey how many can?) shouldn't screw up the desin. However, what's the fuss about Dreamweaver any way? It may be good but at the price they charge it should be. Not a big fan myself and looking at all the most creative designs, they don't use this.