This Option appears is because of security , If you want to off this follow the steps : Goto Option from Menu > Content > Uncheck on Block pop-up windows . (if this checked) This makes allowing all popups open in window without showing the message. Also if you want to do the same for some specific websites , then click on Exceptions in the same box (Content tab),and add the website address which you want appears without any popups.

I have a couple of websites that I go to several pages in. Do I have to list every single one of them as an exception? I do NOT want to allow popups from everywhere to show up but when I list the home page of the websites I do want to allow popups from I still keep getting that "Firefox prevented this page from automatically redirecting to another page" warning. So since Exceptions apparently isn't working to allow the websites I do want to allow how do I stop getting that message?

GordyM said

"Firefox prevented this page from automatically redirecting to another page" "Allow" How do I eliminate this from happening. I want them to open automatically

I've added the url of my homepage to the Exceptions list in every form it could take and the 'won't permit' and Allow button pops up every few minutes. I'm not interested in allowing pop ups on every page I visit. How do I fix this?

I found another posting on this problem further down the page, it's answer is to go to Options, Advanced, General and uncheck the "warn me when this redirects me".