Router question regarding webserver

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Ok, so I have begun setting up my home network using a Linksys 4 port router rather than what I have been doing with a hub and an extra purchased IP from Roadrunner (had two computers needing direct outside access before). Ive gotten myself hooked up and Ive forwarded ports to my computer so that I can have HTTP and FTP access. However, I have one problem: I use OmniHTTP as my webserver, and I have about 3 sites that it servers. In my old setup, it would take the domain that a user entered (I used DynDNS.org domain names) to determine which site to present them with. Now its apparently not getting that information, so all of the sites go to the default webpage (in my log, you can see that where it used to have the site being accessed (such as xanadu.ath.cx), it now just shows "localhost"). What can I do link these back up correctly?