I could use some CSS help...

[Fonz]

Ok not an adult blog but I'm setting up a little mainstream blog where I try to sell some guitars and so.

http://www.drumandguitarshop.com/

I'm having problems positioning an adsense ad. In IE and Chrome it shows up below the posts and on FF it shows up below the sidebar which is the way I want it to be. Any suggestions on how I could chance this so it shows up below the sidebar like it does with FF?

Thanx in advance!