Liquid layout, container troubles

I’m sorry for bringing up another div issue, but I’ve been reading around and i can’t solve it:

This little page displays correctly in IE7, that is with a border wrapped around all the divs, but it doesn’t do that in Opera or FF. And when something is correct in IE7 and wrong other places, it must be really wrong.

The divs are all floated left (except the body) - if I remove the float, the border displays correctly (but messes up the layout). Also, if I float the body (which is the containing element) the border displays, but then the body isn’t centered of course.

I get the feeling that the body isn’t containing my divs, so what am I doing wrong?

EDIT: And if someone could answer me why the left div isn’t at 100% height like they managed to do in the page below, that would also be grrreat: