Firefox

The reality is that to the average user all browsers are the same. A lot of technologies have sort of peaked for regular people and browsers are one of those. There was a time when you needed plugins to do basic things like view PDFs or videos, to play games (flash, java) and there would be a new major change to HTML or CSS every few months etc.

That's no longer a problem. All browsers are near equal in their ability to render pages. So people are naturally going to go with what feels familiar. We lost the battle for market share the minute Google decided to advertise Chrome on their search page.