Here are the steps to set up a port forwarding if you have a configuration like the one below (using NAT). The public (routable/real) IP address is 212.3.4.5, your (web in this case) server’s IP is 192.168.1.10. Since it is a web server, it will listen on port 80.

ip nat inside source static tcp 192.168.1.10 80 212.3.4.5 80 route-map nonat extendable
If you have two or more webservers, you need to assign different port numbers to each port forwarding. It’s good practice to assign a port other than 80 there is no express need for using implicit ports.
ip nat inside source static tcp 192.168.1.10 80 212.3.4.5 1880 route-map nonat extendable
ip nat inside source static tcp 192.168.1.11 80 212.3.4.5 2880 route-map nonat extendable
I the above case, you will access the 192.168.1.10 serer by pointing your browser at http://212.3.4.5:1880 and the 192.168.1.11 by pointing your browser at http://212.3.4.5:2880
The next step is to create a rule to permit access to your server(s). I prefer using a Zone-based Firewall, so my acl-s have sugestive names. I will create an acl that permits access from the intrenet (outside) to the server from the intranet (inside):
ip access-list extended internet-to-intranet-acl
permit ip any host 192.168.1.10 eq 80
The above acl can be translated as: permit access using IP protocol from any source to host 192.168.1.10 on port 80.