Sidebar floating incorrectly–please help!

Hello,
I made some changes to my stylesheet, in an attempt to make the sidebar of my theme a bit more narrow. When I did that, my sidebar moved over to the middle of my page and is now covering my middle section. I tried editing the stylesheet back to its original dimensions, and that didn’t work. I then deleted my modified stylesheet and reverted to the original one altogether, and it still didn’t work. Any advice or suggestions would be greatly appreciated!
http://www.rflib.org (test site, you can see the problem here)

HadleyF80