How to block a site.

I want to deny access to a couple of sites through Squid. We have all
our browsers pointing at our proxy. I believe that what I have to do
now is set up some acl rules? However I have very little
understanding of what is going on there. Can anyone point me to a
step by step reference as to what to do.

Cheers,

--
Simon Bryan                    simon@olmc.nsw.edu.au
Information Technology Manager sbryan@mpx.com.au
OLMC Parramatta