Thanks for the answer.
Yup, it's behind a router and it is already in the DMZ. I'm not sure I understand what you mean with configuring the router to use the static IP. Do you mean that instead of having it route from say 91.xx.zz.yy to 192.168.0.1, it should directly be assigned to 91.xx.zz.yy? Is there no way to get around this? Hosting web pages works fine with the current config and if at all possible, I would like to not have to reconfigure the entire home network.
Oh and in case my first explanation was unclear, I believe what I'm trying to do is basically the contents of the following HOWTO, but without ISPConfig
*How To Run Your Own Name Server With ISPConfig And providerdomain.de (Schlund)*