Oooops

I just loaded and ran avast and everything is working wonderfully. The first time I fired up my internet browser (Mozilla Firefox) I got a pop-up asking to allow or deny…I didn’t recognize the name so I denied. Now I can’t use my browser. I had to turn avast off in order to post this. Is there any way to reverse my decision and allow the browser?

Hi!
Is this popup was given by Firefox, or a firewall (if you use one)? ???

What is your firewall ?
Ensure that it allows ashWebSv.exe, the avast Web Shield.