Firefox Browser, Irritating?

If you have several browsers in your computer like Google Chrome, Firefox, Internet Explorer, Opera installed, are you comfortable for them? Probably, you may say yes for you could open them separately and could multiple Internet job in one setting. In my case, I do avail of them and has made my work easy and fast.

What, however, annoys me is when I open my computer, the instant popping up of Firefox. Have you experienced that? I don't want to uninstall it. What should I do to stop from its automatic opening?