|Do you use Hosts files, if so those website might be blocked? Another possibility is that they are in IE restricted sites (if you use IE).|
Could even be that the servers are down - this can happen.
If you have more than one browser is it the same on them all?
If you are prepared to post any addresses we can see how we get on.
How to know you are getting old 1:
If you can remember when radishes tasted of something