The +1 button used to work with Firefox on external sites but now it doesn't work, it only works within Google+. For example the DailyMail site button for +1 will not work. If you click the button there will be an error. On some versions of the button you can hover over the button and wait for the share option to appear and then you can share via +1 but clicking the button causes an error. The +1 button works fine with Google Chrome. '''I have tried the +1 button on various versions on FF from 11 to 3.6''' the problem is always replicated and it is not an issue with 3rd party cookies being blocked. UPDATE: Oooo, the +1 button just stared working again. I've not changed any browser settings since it was broken so the change must be something Google have done or maybe it was just one of those things.