Modifying DIV height

[Fry750]

Hello all.
I'm trying to recreate a website I did, this time using divs instead of tables.
http://www.brokenrubix.co.uk/stephdiv.html < How can i extend the menu div to the same length of the main content without physically setting the height to the nearest pixel? Is there a way it will automatically change when the content does?
Thanks

 

[Fry750]

Damn, the only real way to do it is to use a background of some sort? I'd have thought there'd have been a MUCH simpler way. Can you explain how i'd do it?