[SOLVED] How to make the center column take the whole width of the page?

Hi everybody,
I started playing around with wordpress / Atahulpa yesterday and now I am stuck with the following problem:
I need a single page without sidebars and the center column should take 100 % of the screen width (to put an an iframe in). I found out how to hide the sidebars, but they still take away space on both sides of the screen.
Any ideas? Thanks for your help!