Upgrade your Squid. 2.5 is rather broken with interception and
acceleration modes.
After upgrading to a later squid. Remove the NAT interception hack.
These two How-To's tell you everything you need to get started.
For reverse-proxy (accelarating) of websites using Squid:
http://wiki.squid-cache.org/SquidFaq/ReverseProxy
For interception of outbound network port 80 traffic:
http://wiki.squid-cache.org/ConfigExamples/Intercept/LinuxDnat
or http://wiki.squid-cache.org/ConfigExamples/Intercept
Amos
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Please use Squid 2.7.STABLE4 or 3.0.STABLE9