Communicating with arduino/ethernet shield through the interweb

Im actually using port 80 as the forwarded port. When I go to example.no-ip(dot)org:80 it serves up the same webpage as is served when i type the ip of the arduino into my browser from my LAN. When I click a html button to toggle the Led it just replies with a "cannot find webpage" etc... Thanks for your reply mate, great people on here.