Help with web server/port forwarding?

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http://askubuntu.com – All of a sudden my web server (i.e. my old desktop computer) stopped responding. I thought it might be a DHCP issue, since sometimes it gets a new IP address (I don't think I have a static IP address hookup), but I double-checked the router ip address (the 192.168.1.something) and the external address by visiting whatsmyipaddress.com or something like that. When I try visiting that ip address (208.120.etc), though, it never responds. Browsing to localhost works fine from the machine itself, and ping 208.120.yadayada works from other machines. I checked the router, and the correct IP addresses ()