As you can see, they block port 80 which is used to host websites. In addition, they limit the amount of bandwidth you're allowed to consume. They also routinely check all computers connected to their network for open server ports.
I'm on Comcast, and their Terms of Service (ToS) actually states that if you run a webserver (or any server for that matter), they reserve the right to cut off your service. I think that's pretty standard amongst cable ISPs, too.
Unless you want to start using DSL, I'd advise against running a web server on your home cable connection.