Q: Trouble browsing

For some reason, I can't seem to get on half the websites I goto when I'm at work.  But when I take my computer home, it works without any trouble at all.

I have tried changing from safari, to firefox and have tried using both hard wire and wifi.  The funny thing is, the other computers at work (which are windows based) goto the same sites without any trouble.  Same internet connection.  There has to be a setting somewhere which isn't configured properly for me.  Any idea's?