there a few ways u can do this. and mostly has something to do with your router.
1. login to ur router : probably
http://192.168.0.1/
2. find the applications or port forwarding settings and have the PC running the webserver or game be forward to the OUTSIDE WAN IP.
or
2. use the ROUTER's DMZ setting
[qoute]
The DMZ(Demilitarized Zone)option provides you with an option to set a single computer on your network outside of the router.If you have a computer that cannot run Internet applications successfully from behind the router,then you can place the computer into the DMZ for unrestricted Internet access.
[/qoute]
now since people can now access your site/pc from the OUTSIDE with your OUTSIDE WAN IP. u also have to remember some ISP blocks port 80 on their client IP. so use 8080 or watever