CSS Help needed VB 403

[shri]

I'm working on a new template and have most of it sorted ... except where there are some floating divs which split the body into vertical columns.
<snip>

The content box ( s5_body_wrap3 ) should close and show the footer below where the groups close and not all the way up, right after the above_content div (which goes all the way across the page).

This happens in both Firefox and IE8, so I suspect it is something pretty fundamental that I've missed.

Any help from those more familiar with vb4's css / divs / boxes would be much appreciated.