LimonSpace here is a open port check tool you can use to test if your ports are properly forwarded:
Open Port Check Tool
Just download it, and follow the instructions on the page I linked you to. Check port 80, and any other ports your game might be using.
If your ports are not open here is a list of all routers, and there port forwarding guides:
Complete List of Port Forwarding Guides
Find your router on there list, and follow there guide to forward your ports.
If and or after all your necessary ports are open, and you still have the same issue it might be because some ISP's (Internet service providers) block port 80. If this is the case you will need to do a port 80 redirect. Here is a guide for that:
So your ISP has decided to block port 80?
And last but not least If the IP that your webserver runs on is dynamic, you'll want to make sure you are running a dynamic update client. Here is a good one that I have used in the past:
Dynamic Update Client for Windows
I hope this all helps <img src="smileys/smiley1.gif" border="0" align="middle">