Hi,i use squid as a web caching server and i configured it to run transparently. my squid version 2.6 on centos 4.6 and i have dhcp giving out ip and other parameters to my lan clients.
i setup acl to block certain sites from being accessed and also certain key words in a url. this is what i did

acl filter_sites dstdomain "/etc/squid/blocked_sites.acl
acl filter_phrase url_regex -i "/etc/squid/blocked_phrase.acl

http_access deny filter_sites
http_access deny filter_phrase

now although its working, iam still having some issues with it. not all the systems on my lan adhere to this rule. like i have facebook blocked but from some systems, i can still access facebook. what do i do?

in the blocked_sites.acl file, i have website like cnn.com,facebook.com while in the blocked_phrase.acl, i have 'mail'

I think you should post all of your http_access and acl lines.