I am new to using a mac I have an older version. But I have used firefox on my pc before. I downloaded it and went to open messenger. Not the full downloaded messenger but the one you can access when in your mail on yahoo. It opened fine but now it won't close, even though I hit sign out again and again. I have tried force quite, uninstalling and reinstalling and still every time I sign into yahoo on firefox there is my messenger list open. For privacy issues I really need to be able to open and close it.