To begin with I should say I'm one of those crazy Mac people, but we have a Linux box running RH9 with IPtables for our firewall at work. We've had a local kid set it up for us but getting timely "adjustments" hasn't been the easiest thing. I've become pretty good at making some changes and I'm looking for a little help on starting something new here.
My boss would like to not allow certain users access to the web. We have two nic's in the firewall and our lan is set up with 192.168.2.xxx that I assign to each computer. Can anyone give me a hint how to start?

Certain users or certain ip addresses?

IP addresses.

Try:
iptables -A INPUT -s xxx.xxx.xxx.xxx -j DROP

Replace xxx.xxx.xxx.xxx with the ip to block.

Thanks David, I'll give that a try tomorrow and post back.