StatCounter gathers its statistics from its own network of users, which encompasses 3 million web pages, leading to 4 billion page views per month. As always, statistics are statistics, so I wouldn't bet your life on them.
As the graph shows, Firefox 3 has surpassed Internet Explorer 7 as the most popular browser in Europe. Of course, if we add Internet Explorer 6 and 8 figures into the mix, IE is still more popular.
Firefox holds a share of 35%, edging out Internet Explorer 7, who sticks at 34%. Internet Explorer 6 still sits at 11%, with IE8 having a share of 2.3%. This puts Internet Explorer's total share at about 48%, and Firefox' at 38% (thanks to Firefox 2.0 users). Opera also does very well in Europe, with a share of 7%. Chrome and Safari are both stuck below 3%.
The figures for Europe differ a great deal from those of the rest of the world. StatCounter's statistics for worldwide browser usage put IE at 62%, Firefox at 29%, and Opera, Chrome, and Safari at less than 3% each. North America has figures very similar to the worldwide ones, but with Safari at 5%, and Opera at less than 1%.
Diving deeper into the European figures, it's pretty clear that my country (The Netherlands) is a bit behind the times, with Firefox at 21%, and IE at 73% - the others barely make a blip on the radar (except for Safari at 3%). It seems like other European countries are the ones doing all the hard work: in Poland, for instance, Firefox' share is at 51%. Opera is doing very well in Russia, with a share of 37% (!).
The figures for operating systems are also fun. In Europe, Windows XP does 69%, Vista 24%, Mac OS X 3.5%, and Linux 1%, which happens to be similar to the worldwide figures. North America is the different one here, with only 0.5% using Linux, and 7.8% using Mac OS X.
As always, these are just statistics, so be cautious.