How to block facebook?

[Moosa]

[Rev]

This depends on if one is blocking a single computer or a whole network. For home networks:
To block it on a single computer, get a web blocking app/addon for all of the browsers running on the target computer. If your home router has a content filter option, you can block fb setting up URL filtering. Be warned that if a home user uses web-based proxies the can circumvent the URL filter. One other way is to subscribe to a public DNS services such OpenDNS which allows you to filter out website by blocking the DNS queries from the Internet Side.