The internet browser market has long been dominated by Internet Explorer, but a new kid on the block -- Firefox -- is making strong inroads against the Microsoft product's dominance. To date, over 75 million copies of Firefox have been downloaded by users around the world. Here are some reasons why you should replace Explorer with Firefox.1. No Pop Ups. Unlike Explorer, Firefox has a nifty pop up blocker in place. No more garbage to fill your screen as you search the internet with Firefox. Can'.