using Belkin Surf N300 Wireless N Router block facebook
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Go into the router settings by typing 192.168.1.2 into Internet Explorer as though it was a network address and at the login page, follow the router's instruction manual as to the name and password you need - sometimes as simple as admin and password.
Find the firewall settings and add facebook.com to the list of sites you want to prevent access to. Apply and Save the settings and log out then restart IE to check it worked.