It probably means that you're not authenticating to your ISP's network or if you have no DSL signal (if you're using a DSL connection. I don't know about cable since we don't have it in New Zealand ). That'll happen if your router has been factory reset, and surprisingly often it happens after a power surge.
Does your router have an "internet" light (or similar) in addition to a "dsl" one? That's an easy way to tell if you have authentication, if it's there.

Otherwise try opening up your router's admin page and checking if the username and password are correct. If you're using DSL, check the DSL status part of the router admin.