|Do you have just the one computer (using a router)? What about a basic ping command?|
Try pinging to a website url like Google, if you don't get reply but something like "Destination host unreachable", it might be a DNS problem. If you do get reply, make sure it's from a valid IP address.
Next try to check if port 80 is open, by using the telnet command:
i.e. telnet google.com 80
Should you get a blank screen, press space and enter. A basic text formation of the site should appear.
"I'm tired. But then again I'm so hungry I can't sleep. But what's the point of eating if your sleepy?" - Sniff, The Moomins.