When using linux as a router you also might want to forwards some ports.
This should do the trick (it will when using my script from the other post):
iptables -A PREROUTING -t nat -i eth1 -p tcp --dport 80 -j DNAT --to 192.168.1.50:80 iptables -A INPUT -p tcp -m state --state NEW --dport 80 -i eth1 -j ACCEPT
But more generally it might be necessary to add an extra line first to allow traffic to your nic connected to the internet at all:
iptables -A FORWARD -i eth1 -o eth0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT iptables -A PREROUTING -t nat -i eth1 -p tcp --dport 80 -j DNAT --to 192.168.1.50:80 iptables -A INPUT -p tcp -m state --state NEW --dport 80 -i eth1 -j ACCEPT