Have you tried conncting from the LAN? Maybe your ISP blocks connections to port 80 themselves?

Also because you may have errors in the firewall config, try just removing all ipchains rules altogether, then try.

Get it working on a LAN, without the firewall, then make sure the firewall is working right, then try from elsewhere. The ISP may block all ports below 1024 or something if they're really paranoid, so try a high port number instead (8080 is popular)