[squid-users] ACL's

Hi,
I am trying to set up ACL's
I have started off with a fresh install
of Mandrake Linux 9.0 kernel 2.4.19-16kdk
and am running Squid 2.4.STABLE7
Squid does run and I can access the internet
using it.
What I want to do is set it up for a local school
so that the only sites the students can access are
ones which the Tutors consider they should use.
I am getting strange behaviour.
If I add this acl:
acl nogo dstdomain .com

and this access:
http_access deny nogo
I can get to some .co.uk sites but not others
also I sometimes get the expected
404 not found message but other times
I get the home page of my own site
( not on my local PC but a genuine internet site)
but without any images, displayed.
Also sometimes I can still access *.com sites
I am guessing that there may be some problem
with DNS lookups but cannot see how I can
set it up so the students could, for example,
access all IBM sites and all Netscape sites
but no other sites.
Any idea what is wrong please?
And can someone give me the required
acl syntax to allow use of a file?
tia,
norm

-- 
http://www.nelliott.co.uk
registered Linux user 277766