At home we have a proxy server. At work we don't. Firefox irritates in this regard: whenever I launch it, it defaults to the proxy server. If I do Tools>Options>Settings and select "No proxy", no problem. However, if I shutdown Firefox and restart it, I have to do the Tools>Options>Settings thing all over again because the "No proxy" setting doesn't "stick". 

How do I make it stick? Alternatively, can someone suggest a bit of javascript that I can assign to a button on my toolbar which will toggle between the two states?