Even a webmaster usually accesses the 'net through an ISP, so his IP address will probably change each time. IP address is not a good screening tool.
You could drop a cookie on his hard drive to "mark" or identify him; but how long would it take a "webmaster" to figure that out and delete it or block cookies?
If the rougue links he or she is entering are links back to their own websites, then you can keep a database of domains that are "blocked", as Kirk sugested.
It is really hard to identify individuals over the Internet, especially if your server is wide open. You could have some type of user authentication (user id & password) that you can revoke if they post something bad. If you don't want to go that route, then the next best suggestion is to add an "approved" flag to your tables and don't display anything unless that flag has been set. Just let people know that it might take a day or two before their posts are approved and show up on the site.
-- Rich Rijnders
-- Irvine, CA US
