List of GPS's compatible with Firefox 3.5?

"Perhaps a better resource: Geolocation in Firefox (by Mozilla)
TLDR: no gps is being used
How does it work?

When you visit a location-aware website, Firefox will ask you if you want to share your location.
If you consent, Firefox gathers information about nearby wireless access points and your computer’s IP address. Then Firefox sends this information to the default geolocation service provider, Google Location Services, to get an estimate of your location. That location estimate is then shared with the requesting website.
If you say that you do not consent, Firefox will not do anything.

How accurate are the locations?

Accuracy varies greatly from location
to location. In some places, our
service providers may be able to
provide a location to within a few
meters. However, in other areas it
might be much more than that. All
locations returned by our service
providers are estimates only and we do
not guarantee the accuracy of the
locations provided. Please do not use
this information for emergencies.
Always use common sense.

What information is being sent, and to whom? How is my privacy protected?

Your privacy is extremely important to
us, and Firefox never shares your
location without your permission. When
you visit a page that requests your
information, you’ll be asked before
any information is shared with the
requesting website and our third-party
service provider.
By default, Firefox uses Google
Location Services to determine your
location by sending:

your computer’s IP address,
information about the nearby wireless access points, and
a random client identifier, which is assigned by Google, that expires
every 2 weeks."