Asking you for your location is a feature of Firefox and not of the website alone. So the prompt you are being sent is actually a feature of Firefox. This means you cannot have Selenium turn it off.
Selenium does have the ability to open Firefox with a specific profile. So you could run Firefox with the -P option, create a Selenium specific profile. Then edit the profile to turn off geo.enabled. Save the profile and use that profile when you start up Firefox. If you go to
https://code.google.com/p/selenium/wiki/FirefoxDriverInternals it is a good starting point on how to use custom profiles. As for the change to disable geo location:
- Open Firefox
- Enter about:config in the address bar
- Find geo.enabled
- Double click the entry
You should now have geo.enabled set to false.