Google's Chrome overtook Apple's Safari to become the world's third-most popular browser just 16 months after its debut, according to measurement firm Net Applications.
Microsoft's Internet Explorer (IE), meanwhile, lost almost a full percentage point in December, bringing it down to a new low of 62.7 per cent.
Chrome ended December with a share of 4.63 per cent, according to California-based measurement firm Net Applications. Apple 's Safari, which dropped into fourth place for the first time, posted a share of 4.46 per cent.
Chrome's December increase of 0.7 of a percentage point, the largest since Google launched the browser in September 2008, may have been partly fueled by the release three weeks ago of beta editions for Mac and Linux.
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 per cent 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 per cent, delaying for at least another month the No. 2 browser's move past the 25 per cent milestone.
As has been the trend for years, Microsoft 's IE again made the biggest move of any browser: It dropped 0.92 of a percentage point to 62.7 per cent, a new low for the application that once held a share well north of 90 per cent.
Even more troubling for Microsoft is IE's quickening decline. IE lost an average of 0.94 of a percentage point in each of the last six months of the year, nearly triple the 0.36 of a point average during the first six months. Notably, the slump came in the face of the availability of IE8, which went final last March, showing that - at least so far - Microsoft has been unable to stanch IE's losses.
Microsoft continues to make headway in its campaign to convince users to abandon the eight-year-old IE6 for IE8, however. When Net Applications accounts for IE8's "compatibility view" - a feature that lets users display sites as rendered by the older, and often Web standard-incompatible IE6 and IE7 - Microsoft's newest browser owned a 23.7 per cent share, compared to IE6's 21 per cent and IE7's 15.5 per cent shares.
December marked the first time that IE8 was the most-used Microsoft browser. When the compatibility view data is included, IE8 accounts for 37.8 per cent of Microsoft's total browser usage share. IE6, previously Microsoft's No. 1 edition, fell to the second spot with 33.5 per cent of IE's total.
IE7's number fell farther than IE6's last month -- the former dropped 1.3 percentage points, the latter, 1.1 points - additional proof that IE8 has stolen much of its share from the more modern IE7. Since IE8's March launch, IE6's share has declined 10.4 points, but IE7 has lost almost twice that, falling 19.6 percentage points in the same period.
The relentless decline of IE has been a boon to rivals, of course, which have collected new users at Microsoft's expense. The shares posted by Safari, Chrome and Opera were all records, for example.
Projecting IE's slide using Net Applications' data, Computerworld now estimates that the browser will fall under the 50 per cent share mark as early as mid-May if the dramatic negative trend of the last three months holds true.
Like Microsoft, Mozilla did a good job last month converting users to its newest browser, Firefox 3.5. Fewer than 7 per cent of all browser users ran Firefox 3.0 in December, for example, a decline of 1.2 points, the largest dip since September 2009.
The jump in Firefox 3.5 usage may be in reaction to the impending retirement of version 3.0 later this month, when Mozilla will stop serving up security updates for the older application.
Net Applications measures browser usage share by tracking the systems used to visit the 40,000 sites it monitors for clients, which results in a pool of about 160 million unique visitors per month.
December's browser data is available on Net Applications' site.