Sidebar and Main content area are full height when the site opens but when you scroll they don't reach the bottom...please HELP!

Please help! I can't get the lefthand sidebar and main content to be the exact height. What am I going worng.

I have been strugling with this problem now threedays trying everything and I have turn to guys as my last hope.

Here is the link to the site http://buki.tstage.co.uk/

Kindest regards

Dominic (