Dart Board
Register a protocol in Firefox under Linux

Awesomesauce: http://kb.mozillazine.org/Register_protocol
I recently ran into trouble after I installed Spotify. Then I tried to open a Spotify link which look like this:

 spotify:user:spotify:playlist:2lusnaAIIckVJJFKM2upO

Which gave me “The address wasn’t understood” from Firefox. Took a while as most spotty users aren’t exactly Linux hackers. It took me a while but I found the Tutorial above. Which said go to your favourite terminal and

 gconftool-2 -s /desktop/gnome/url-handlers/spotify/command '/usr/bin/spotify %s' --type String
gconftool-2 -s /desktop/gnome/url-handlers/spotify/enabled --type Boolean true

(well I changed what he had to spotify)

Solution in windows: Add a registry key. Enjoy if your stuck in that OS.