What was once unbelievable and would cause a storm of anger just 5 years ago has happened. The once unbeatable Firefox which freed us from the stranglehold of IE 6 is about to the point of being irrelevant to webmasters.
Firefox is now at 10% where it is safe it ignore for many webmasters. What changed was IE finally being mediocre and of course the rise of Chrome and webkit browsers and applications through mobile platforms which has exploded growth in the past 5 years as well.
What is not helping is Firefox losing many users each release over the year starting with 4.0, constant updates which break addons, removal of features, and copying Chrome and adding social media and webcam functions, while Chrome kept adding more HTML 5 and CSS 3 features at the same time.