margin or width difference between firefox and ie?

Hi — I have a width difference between these 2 browsers that I can’t figure out for the life of me. Here’s the page:

My site.

If you look in firefox, the dotted line at top of page (just below the “show/hide this section”) ends on the right top corner as it should.

In IE, it keeps going and the “show/hide this section” text is cut by the border. I have played with this for soooo long and can’t figure out the cause. Your help is greatly appreciated.