More and more people have recently discovered that using DIV+CSS is called to represent XHTML. This is fundamentally not true!
First, CSS is a technique called style sheet (stylesheet). Some people call it cascading style sheets (cascading Stylesheet), and Div is a label in HTML. div and table are siblings, so you should not link div with CSS to represent XHTML.
Second, DIV+CSS does not necessarily conform to standards, XHTML and not just div+css. Many sites or forums that claim to have used div+css for refactoring do not in themselves pass the w3.org checksum. (For example: moving the network forum and Vtbbs cannot pass the w3.org XHTML checksum at all.) Even through the verification is only to show that it is grammatically correct, a considerable number of sites are also suspected of abusing div.
So please don't be overly obsessed with div+css.