I just read on heise.de that the Google Chrome Web-Browser is used by more than 43 percent of the requests. This is a plus of six percent in relation to the beginning of 2013. On the second place is Microsofts Internet Explorer :(. But it lost 5.7 percent in the last six months :). That is very good for every web developer, cause too much time is needed to support this browser, although it is getting better.
The statistic has 15 billion page requests as base due to Statcounter. They are divided between 3 million different websites. The full article can be found on heise.