hello friends needed a small help

[gin_oy]

is there anyway we can block certain wesites in a network. I mean the block should be such that if necessary the admin/ or a set of people can acess the sites from any computer connected to the network..

In my college the block is such that u cant directly open orkut.com but if theres something like orkut.com/xyz then it can be opened.
a block like this will also do.

[kiranbhat]

google it