[Cyber_old]

Obviously, you can't block port 80 otherwise you will not be able to access web sites via the browser. Port 7777 is used for San Andreas Multiplayer, port 21 is FTP, 6969 is a port some people use for like Teamspeak servers, gaming servers, etc, 25 is outgoing mail (most ISP block it anyway, due to spam). That being said, it's probably not a good idea to block all of these ports.