Blocking port 80 means no internet connection, unless that is your plan to secure your pc, then as nikorr says, go in to firewall and block all inbound and outbound traffic.
Why would you want to block HTTP? Theres no reason to...
To further, closing port 80 only blocks your HTTP server (if you set one up). If you set up a server, I would hope you would know how to manage your ports. Your web browser connects from a random open port in the 40-50k range to a server on port 80.