Not so long ago, when you selected "Update" in the "Help - About Firefox" Menu, the browser would close by itself after it had downloaded the update when you clicked on Restart and sometimes if not always required accepting a UAC popup and after updating, the browser would restart and all tabs that were open would re-open (normally). For some time now, clicking on Restart just restarts the browser and the only way for the update to occur is to close the browser and so all tabs are lost upon restart. Why does the Restart button still appear when it no longer works? This is rediculous. The functionality of the button has been broken for quite a few updates now. Why?!
