Internet Explorer's market share plunged by a record-setting amount during December, according to web metrics vendor Net Applications.
Microsoft's browser lost 1.6 percentage points of its market share last month, ending December with a 68.2% share, down from November's 69.8%. Since the end of October, IE has lost 3.1 percentage points, nearly half of its total 2008 losses.
IE ended the year down 7.9 percentage points, a 10.4% decline in its share since December 2007.
Not surprisingly, the bulk of IE's December loss came from IE6's declining popularity; the older browser, which first appeared in August 2001, has long lost share to the newer IE7. However, IE7 also slipped significantly. Microsoft's newest production browser dropped 0.6 of a percentage point last month, the largest slip since its October 2006 launch.
Microsoft is currently working on IE8, and has said a "release candidate" build of the browser is "just around the corner."
For the second month running, rival browsers from Mozilla, Apple and Google all gained ground at IE's expense, according to Net Applications' data, which is culled from visitors to the thousands of Web sites the company monitors for clients.
Mozilla's Firefox, which climbed above the 20% mark in November, increased its market share by another 0.6 of a percentage point to finish the year with a 21.3% share. During 2008, Firefox's market share climbed 4.5 percentage points, an increase of 27.3%.
Apple's Safari posted even more impressive gains during December. The browser, which is included with all Macs, increased its share by 0.8 of a percentage point, its largest one-month increase ever, to end the month at 7.9%. Safari's share has grown 41.9% since this time last year.
And Safari set a two-month record increase at the end of 2008. The 1.36 percentage point gain during November and December was nearly double the previous record, a 0.72 percentage point increase in September and October 2006.
Google's Chrome, which debuted in September and left beta testing in early December, also boosted its market share, ending the month above 1% for the first time.
In the last two months, Firefox and Safari have grown nearly identical amounts, gaining 1.37 and 1.36 percentage points, respectively, during November and December 2008.
As it did last month, Net Applications again argued that at least some of the decline of IE - and the corresponding increases by Firefox, Safari and Chrome - was due to the calendar. "The December holiday season strongly favoured residential over business usage," the company said on its Web site. "This in turn increases the relative usage share of Mac, Firefox, Safari and other products that have relatively high residential usage. All December usage statistics should be read in that context."
According to Net Applications, usage of non-Microsoft browsers climbs after work hours, on weekends and during holidays, as users surf from home computers rather than from work machines, which are far more likely to run Microsoft's IE.
While December and November have traditionally been tough months for IE - perhaps in large part because of the large number of off-work days - 2008 was, by far, the worst for Microsoft's browser. The 3.1 percentage point loss in November and December 2008 was significantly larger than other years' declines. In November-December 2007, for instance, IE lost 2.3 percentage points; and in the same two months during both 2006 and 2005, the browser lost 1.5 percentage points.
Of the top four non-Microsoft browsers, only Opera Software ASA's flagship application failed to grow its share; it stayed at 0.71% in December, the same as in November.