IE 6 and 7 Issues, Pushing Middle Content Below Left Column

Hello,

I am working on the site: www.csf.net and I am using the Forest Floor theme.

I am having issues similar to others here, where my center content and the right column are being pushed below the left column. I have tried to add the overflow: hidden; tag to the left, right, and main columns, but no luck.

http://csf.net/themes/forest_floor/style.css
is the CSS code for the site.

Any advice would be most appreciated. Thanks!

-Zeb