To see if you've done the port forwarding correctly, go here:
http://www.yougetsignal.com/tools/open-ports/
Click on "Check" (it should default to port 80 and your IP). If it says the port is open, then you're good. If it says the port is closed, something went wrong with the port forwarding. Also make sure that you've got exceptions in any software firewalls you may be running on your PC.
Also, try typing "127.0.0.1" (also known as localhost - this is essentially the address for the machine itself) into the address bar of your browser. You
should see whatever is hosted on the webserver - it should be working correctly. If it's not, then something is wrong with the configuration of the webserver (regardless of any port forwarding).