Since HTTP uses port 80, and that one is used by your ASUS Wl700gE, your PC has to use another port.
i.e. if you access your web as
you would access the other PC's web server as
You just need to find the free port and set it up on your Linux PC's web server.
Then second action would be to create (i think they call it) virtual server on ASUS. That would forward all enquiries for port 8080 to the PC, not router.
I'm at work right now so I don't have ASUS in front of me so I can't have a look.
But basicaly, you say, WAN port 8080 maps to the ip adress of the PC and port 8080.
Or If I'm not mistaken, you could just leave PC to port 80, and just map WAN port 8080 to PC's Ip adress port 80?
I can have a look when I get home if you don't manage