Firefox ignores language settings

Wed Oct 5 16:32:49 UTC 2005

For webpages which are available in different languages the preferred
languages can be set in Preferences/General/Languages. Unfortunately
this does not work for me. Although I have set de-de (German) as
prefered language the page
http://www2.uibk.ac.at/fakultaeten/
is always displayed in english. I guess the problem is that the browser
identifies itself as
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.7.12) Gecko/20050922

As you can guess I have an english version of firefox installed. Is
there a way to change the browser identification string?
Or could the problem be located somewhere else?