Internet Explorer posted another major gain in share last month, the second in the first quarter of the year, perhaps signaling a turnaround in Microsoft's fortunes, a Web metrics company said Sunday.

Meanwhile, every rival, including Google's Chrome, which is usually the one stealing users, lost share.

Internet Explorer (IE) gained 1 percentage point during March, said measurement firm Net Applications, to end the month with a 53.8% share, its highest level since September 2011. Last month's growth was the second this year of 1 point or more.

Chrome lost a third of a percentage point to close March with 18.6%, while Mozilla's Firefox slipped by about the same to 20.6%, the open-source browser's lowest number in more than three years.

Apple's Safari and Opera Software's desktop browsers also dipped, falling by two-tenths and one-tenth of a point, respectively, to 5.1% and 1.6%.

Chrome's decline is especially notable, as March's slide was the third consecutive month that Google's once-hard-charging browser lost share. In the first quarter of 2012, Chrome has dropped more than half a percentage point, representing a 3% decline from the browser's December 2011 number.

Previously, Net Applications has attributed Chrome's skid to Google's January demotion of the browser's search ranking and then last month, to recalculations that eliminated the extra activity generated by Chrome's pre-rendering feature.

Google restored Chrome's search ranking last month.

It was unclear whether the rise of Internet Explorer (IE) and the fall of every rival was due to a rejiggering of Net Applications' numbers.

Like most Web measurement firms, Net Applications has more data on some nations -- the U.S., for instance -- and relatively small samples from others, such as China. To produce what it believes is a more accurate representation of global browser usage, Net Applications weights its Chinese data proportionally higher because that country has a greater percentage of the world's Internet users than the U.S.

Net Applications uses online population numbers provided by the U.S. Central Intelligence Agency (CIA), which has regularly tracked big jumps in China's part of the browser-user pie, and corresponding drops in the percentage of the world's users who hail from the U.S., Europe and other developed countries. Earlier this year, a company spokesman confirmed that it would revamp its calculations with newer CIA numbers at some point.

In February 2011, after Net Applications' last accounting change, IE's usage share jumped an eighth of a percentage point, at that time its largest one-month increase ever.

Because Chinese users overwhelmingly rely on IE, or a modified version of Microsoft's browser, the country can easily skew Net Applications' share estimates toward IE as more people there access the Web.

Microsoft, not surprisingly, applauds Net Applications' country-by-country weighting system, going so far last month as to explicitly challenge the accuracy of the data from another metrics company, Ireland's StatCounter, which also publishes monthly browser share numbers.

Net Applications did not reply Sunday to questions about whether it revised its weighting formula last month, and if so, what impact that had on IE's share.

Microsoft mentioned the overall gains of IE in passing on Sunday, but as it's done for months, focused on increases of Internet Explorer 9 (IE9).

"We ... see great strides made against our core metric: IE9 against Windows 7," said Roger Capriotti, director of IE marketing, in a Sunday post to a company blog.

Almost since IE9's debut, Microsoft has ignored IE's aggregate performance -- which admittedly has been dismal until late -- and instead focused on the growth of its newest browser among Windows 7 users, a combination the company has regularly claimed is the only measurement that matters.

By Net Applications' numbers, IE9 accounts for 34.5% of the world's browsers used on that operating system, an increase of more than four percentage points from February, and owns a 48.9% share of the Windows 7 browser market in the U.S., a jump of 8.5 points.

The browser's global share of all operating systems, however, is significantly lower, at 15.2%, but even that was a bump of 2.6 percentage points, the largest single-month gain since IE9's March 2011 launch.

Other editions of Microsoft's browser didn't fare as well: IE8 lost 2.5 percentage points to fall to 25.4%, while IE7 dropped to 4.5%. IE6, the nearly 11-year-old browser that Microsoft has been trying to bury, stayed flat at 6.9%.

StatCounter, however, told a different tale.

The Irish company, which neither adjusts its statistics for each country's online population nor discards Chrome's pre-rendered pages, said that IE controlled 34.8% of the browser market, down nine-tenths of a point, while Chrome grew by more than a point to end March at 30.9%. Firefox, said StatCounter, remained stable at 25%.

Net Applications calculates browser usage share with data obtained from more than 160 million unique visitors who browse 40,000 Web sites that the company monitors. More browser share figures can be found on the company's site.

Internet Explorer share has ticked up this year, while Chrome has lost a little ground. (Data: Net Applications.)

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is gkeizer@computerworld.com.

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