http://www.computerworld.com/s/article/9222322/Chrome_edges_Firefox_grabs_second_browser_spot
So depending on whom you believe, it either just happened or will in a few months. An impressive rise.
In September, Computerworld used StatCounter's numbers to project that Chrome would pass Firefox no later than December 2011.
According to StatCounter, Chrome has gained 10.8 percentage points of usage share this year alone, vacuuming up nearly all the losses posted by Firefox (5.5 points) and Microsoft's Internet Explorer (6.3 points).
Internet Explorer (IE) accounted for 40.6% of all browsers used last month, StatCounter said.
Rival Web measurement firm Net Applications saw the Chrome vs. Firefox tussle differently. Its tracking put Chrome behind Firefox in November, controlling 18.2% of the market compared to Firefox's 22.1%.
But if both browsers keep to their recent trends in Net Applications' accounting, Chrome will pass Firefox in April or May 2012 to slip into second place behind IE. By that time, IE's share will have fallen to 47%-49%.
So depending on whom you believe, it either just happened or will in a few months. An impressive rise.