Perhaps I wasn't clear. It's not the white background, it's the patterned background to the right and left of the content area. To be more precise, they have two div's with class "skinClick" setup on the right and left of the "content" div. You click on either one of those and it's the same as having clicked on the ad just below the nav-bar.

I tested in Safari, Firefox, IE and Chrome, same behavior. There's also the "Wait, your page is loading" popup ad you mentioned.