The other part of this is that you will need to configure your browser to point to the proxy server. If you are trying to enforce this for a site with lots of people the firewall is typically setup to deny access on port 80 from anyone except the proxy server. This forces the users to use the proxy.
Alternately, do transparent redirection so all requests for port 80 are sent to the proxy. This does *force* the users to go through the proxy, which of course has both good and bad consequences.
Cheers,
-- Rodolfo J. Paiz rpaiz@xxxxxxxxxxxxxx http://www.simpaticus.com
