how can we Block social networking sites or know when sites are accessed

[P A Thomake]

to block social networking sites,and to know as example in collage campus any student use the facebook or any social networking site then suddenly the college system knows about that and block or ban this.........

[Anas Mosaad]

Define a rule in your collage firewall to block the required sites. Not sure why you ask this question in C/C++ forum. It should have been in the networking forum http://bytes.com/topic/networking/.

Some firewalls allow you to display a message that site abcd.com has been blocked.