Internet Explorer is only #1 because it already comes on your computer. Most people that use IE don't have the "know-how" to install browsers like Firefox, Chrome...etc., let alone don't even know they exist or what they are. I work in a public library and it's frightening to see how technically savvy so many people aren't. In the beginning though for Firefox at least, compatibility was always a problem for most websites although for the most part, that problem is almost a thing of the past. I noticed that with the new OnLive cloud gaming service, though, only IE and Firefox are supported.