A lot of certain things in Internet Explorer don't appear or work like they do in every other browser.

There may be other things, but these are the prominent problems I can find clearly that make the biggest impact:
- White main container table is moved to the far left of the screen instead of moving to the center and taking everything else along with it.
- Hyperlink appearance hasn't changed to the customised colours or style.

Like I said, as far as I know this is only a problem with the Internet Explorer browser. Other browsers I've used and know the above works in them are:
- Firefox
- Chrome
- Safari

http://validator.w3.org/

plop your url in here and check the results.

It's often the result of bad code. Unclosed items, etc

Sorted, thanks Rev. Voodoo.