safari question

I recently switched to an IMac from a pc. I love the functionality but have a question about safari. Random sites don't seem to work and when I go to "top sites" they are all white with an access denied on them. if i click on one, it goes back to the site where i was before. I am confused. This is a employer owned mac...could it have to do with security on it? thanks

The "access denied" may be because the top site link (link?) is directed to a page that you have to log in to and your session will have expired. Are those pages in Top Sites linked to something that you generally have to log in to?