[squid-users] yes or no question

[Alex]

Good day.
I've checked Russian FAQ and did not find the answer to my question. 
I have a net with 20 computers. I want to block access to certain sites
forbid to download of certain types of files (*.mp3, *.avi e.t.c.).
Is it possible with Squid? For now I just want "yes" or "no" because the
rest I'll try to find myself.
Regards, your potential user.