Right border not showing up

Hello,

I am working on a School website on the content box the right border is not showing up on some browser.

Here is the picture of what I am talking about http://abkdesign.com/border.gif. The red arrow is pointing to it.

The url of the site is http://whhs.guhsd.net to look at the code.

How can I fix that?

Thanks

Looks fine to me in IE6/Win (can see the borders).