Mailto links to Google Apps Gmail in FF3

http://techblog.appirio.com/2008/08/defaulting-your-mailto-links-to-google.html
http://www.addictivetips.com/internet-tips/easiest-way-to-set-gmail-as-default-firefox-3-mail-client/

Go to
about:config
and set the following settings to true:
network.protocol-handler.external.mailto
gecko.handlerService.allowRegisterFromDifferentHost

When on gmail page, go to (replace lichner.name with your domain):
javascript:window.navigator.registerProtocolHandler('mailto','https://mail.google.com/a/lichner.name/mail/?extsrc=mailto&url=%s','Google Apps')

Click Add Application button that should appear in top right corner.

If the button doesn't appear, make sure that quotes are not replaced with smart quotes. If it still wouldn't work, try it in save mode:
firefox -safe-mode