In a related note, Quark recently redesigned their site using XHTML for structure and CSS for presentation and table-free layout. The pages are simple and beautifully clean. The main navigation features slick slide-down subnavigation, though they could have built this navigation using an unordered list, then kept the subnavigation properly nested within the main nav list. The majority of their top-level pages validate using XHTML 1.0 Transitional.
Visitors hitting the site with older browsers (such as Netscape 4) are given a popup window recommending alternative standards-compliant browsers. We tend not to like this approach as much because of the potential use of bug-ridden or poorly written browser detection scripts which may exclude the wrong suspects, unnecessarily confusing some users.