Firewall 1 muliple websites behind firew

I’m running Firewall-1 with exchange 5.5 behind the firewall people can acess exchange via http but when i setup a site on a differant server with IIS i cannot get to browse it they always end up on the exchange server. I’ve setup NAT and routing and work station with no result. Can anyone Give me a step by step Procedure to get my hosting right.