This just started in the last week. I have not had this problem before and I went back into the Options settings to make sure the box was checked.
Specific web sites repeatedly?
Or do they seem to be random websites?
I just opened my Mozilla browser and went to email, clicked on the notification that I had a reply to my question, and this window popped up: http://newsdaily7.com/jobs/?t202id=62361&t202kw=us.mg4.mail.yahoo.com This "newsdaily7.com" been one of the ones I have seen before.
And you are using Yahoo Mail thru Firefox?
Do all those popup windows show that =us.mg4.mail.yahoo.com at the end of the URL, or something similar?
If so, I can't only guess that Yahoo Mail is getting around the popup blocker.