The good the bad & the ugly - CSS, columns & relativ

OK here is a tricky one. I am relatively new to the world of CSS so I apologise if this is blindly obvious.

My problem is this. I am trying to build a CSS only website that has two columns. The design has a header, a footer, a side menu and a content area. Not too bad I hear you say... CSS can do columns. My problem comes because this site has also got to be WAI AAA accessible. One of the rules says that you cannot used fixed values. In other words my two columns cannot be fixed width. This gives me a little problem with my footer. If you go to:

http://headserver/headscapesb/accessible/index.asp?PageId=1

you will see the design kind of working. The problem I have is when the amount of content is less than the height of the right hand menu. Go to:

http://headserver/headscapesb/accessible/text.asp?PageID=23

and you will see the problem. Basically the footer bar disappears behind the menu instead of being forced down to the bottom of the menu as it would if i had used tables. Can anybody help.