Last time I checked, their markup was pretty much nightmare fuel, but it should work fine with IE5, I'm sure :)
Nowadays it's fine for a webdev to not test their pages on IE5, but when the page is done right, there is no reason for it not to work in IE5, lynx, w3m or Netscape Navigator. Really, it's just a webdeveloper's job done right.
I've seen plenty of idiotic examples of tables being implemented with a bunch of styled <div>, probably because people keep parroting the idea that tables are bad because table based layouts are bad.