According to global analytics website StatCounter, Firefox 3.5 has edged past Internet Explorer 7 as the most popular browser on the market today.
Keep in mind that the stats in question are differentiating by version, so it's actually kind of a lucky swing for Firefox at the moment, as Internet Explorer users continue to migrate from IE7 to IE8. (IE8 will most likely surpass Firefox 3.5 shortly.) If we were comparing browser share but ignoring version numbers, we'd be looking at a very different picture (though IE continues its steady decline while Firefox and Chrome usage appears to be steadily growing). Either way, it's a small victory for the non-default browser market.