I noticed you have more than one stylesheet being added to the page. I didn't bother counting how many in total because your scripts are a mess, but you should check and see if the missing styles are coming from one or several in particular. That would narrow down the problem a bit at least.
I am viewing in IE9. It looks like some things are missing, since the colors appear quite mismatched in some areas. The layout isn't really collapsing or anything, so there is obviously plenty of styling still happening.