Why Isn't My Firefox Working?

[Tiffany]

My firefox stopped working yesterday. I double clicked it and it got this little grey dot at the bottom of the icon, but it wouldn't open. Now it's just a grey question mark, and still won't open. Why isn't it working, and how can I make it work again?

Btw: I'm on a Mac, and I don't know how I installed it, my friend did it for me.

[ProfGene.Togolot]

It might have Malware on it or a virus. Try uninstalling it in Control Panel Programs Uninstall and then reinstalling it and if it still doesn't work you run some good anti-virus software.