If you work for 'the man' and are trying to view them on his interweb, expect it to be on lockdown.
Many firms block sites like YouTube, eBay, HotMail etc as they believe that you can't be trusted and must be slapped into line. Plus you may not be able to download the software you need to see the vids.
If this is the case, go and call your director a w@nker and slap him about with a large wet haddock. You'll get fired, obv, but then you can use the computers in the library to view YouTube, and while the money on the social is cr@p, at least the hours are good