right two columns move left when maincontent column has not content

[deronsizemore]

www.kentuckygolfing.com

It's not a huge problem, becuase I don't know of a situation when my #maincontent section has not content, but just in case that ever would happen, I'd like to go ahead and get a fix for what's happening. As you can see there is not content in #maincontent and the right two columns are shifted left where the maincontent area should be. When the maincontent area actually has content, everything is fine.

What do I need to add/change in my stylesheet to make the shift not happen when there is no content?

EDIT: Looks like this is only happening in FF also.