I downloaded Firefox (the 15 verison, which is the latest version). I didn't like it since it was kinda slow, so I switched to the older version. I currently have the 3.6.28 version of Firefox. However, there is a pop-up that keeps popping up when I open Firefox. The pop-up warned me to upgrade. I really don't want to upgrade to the newer version because the older version is REALLY fast. What will happen if I don't have the latest version of Firefox? Will this give me any bad viruses because the older version doesn't have full protection?