Internet Explorer (IE), meanwhile, lost almost a full percentage point in December, the latest slip in a decline that accelerated during the second half of 2009.

Chrome ended December with a share of 4.63%, according to California-based measurement firm Net Applications. 's Safari, which dropped into fourth place for the first time, posted a share of 4.46%. The swap in positions came a month earlier than Computerworld 's December prediction, which had been based on a three-month gain-loss trend of the two browsers.

Chrome's December increase of 0.7 of a percentage point, the largest since launched the browser in September 2008, may have been partly fueled by the release three weeks ago of and .

Although it fell to the No. 4 spot, Safari didn't stand still last month: It picked up 0.1 of a percentage point. Opera Software's flagship browser also gained ground in December, and accounted for 2.4% of all browsers used in the month, a record for the Norwegian-made program. However, Mozilla's Firefox lost 0.1 of a percentage point, finishing with 24.6%, delaying for at least another month the No. 2 browser's move past the 25% milestone.

As has been the trend for years, 's IE again made the biggest move of any browser: It dropped 0.92 of a percentage point to 62.7%, a new low for the application that once held a share well north of 90%.