Sir Dong,
If naggamit mo og server systems (eg.: kerio, etc), you can block it from there.
Nya pwede ra nimo i-block or i-allow by user names or user groups if you want to.
If wala moý ingong ana, palit og router nga naay some sort of website blocking module.
You can block websites by url or by keywords, depende sa imong mapalit nga router.
Parehas ani o:
Code:
http://www.wikihow.com/Block-Unwanted-Site-From-Your-Router
At least, with either of these 2 styles, you can block websites without doing it individually on each PC terminals.
I hope this helps.