CSS or Cascading Style Sheets have some amazing implications to help the SEO create better optimized pages without tables in addition to a fluid and clean design that not only helps visitors put helps search engines get to the content of your page. There is a very good thread on Crea8site Forums I wanted to highlight as its got some gems to take away for those that use CSS to design websites. Barry Welford started the thread with a tip that helps many browsers deal with DIV tags by using a containing block to help get the positioning right. He says "It's so simple too. It's always to use two divs one inside the other." He goes into detail that his tip works well for many browsers such as Firefox and IE that might treat the width, padding, and borders differently.
Some of the members go into detail why this is and not useful in most cases. Adrian goes into saying that unfortunately we wouldn't need to use the hack unless all browsers handled div's correctly, basically stating that the hack is using 2 div's to do the job of one. Most designers I run into don't go as far as the hack mentioned in the thread but instead use container div's for overall page layout as Adrian mentions. There are some good posts and information from some experts on how they design. Plus some nice resources for other sites to help with CSS. Felt this thread deserved a mention for its great content.