It's really hard to say where the problem is. There's about a 50/50 chance wither way. It could be that the server you are trying to access simply didn't respond, or that your own ISP is having some connectivity issues.
Is this a once in a while time out issue? If you click refresh after you get the time out, does it time out again? Or does it simply never load?
One thing you might try is pinging the ip address for the site and see what happens. That will let you know if you're communication with the server at all.
Are the sites you can't access all hosted at the same place, or just various servers here and there?
art.googlies.net - personal website