IE not working

I have a PunBB forum on my school's server that I am making... and it appears to be working great on all browsers except for Internet Explorer for Windows. It just looks all messed up, to the point that it is unusable.

The address is http://www.ishonline.tk

I have heard that frames (like .tk) can affect PunBB, but why only in IE?

I'd really appreciate it if you take a look at the site, and maybe look at the CSS to see if  something is causing this problem there.

Thanks,

Reuben.