March was a big month for Web browsers, with major new versions of both Internet Explorer and Firefox. Both browsers have been suffering in the browser wars; Internet Explorer has steadily declined from its near-total monopolization of the browser market, and Firefox's growth has faltered, most likely due to strong competition from Google's Chrome.

With Internet Explorer 9 out for just two and a half weeks, and Firefox 4 available for only nine days, however, not much has changed so far. Microsoft's browser continues to shed market share, dropping 0.85 points to 55.92 percent. Firefox is essentially unchanged, at 21.80 percent. These new browsers may yet be influential in encouraging people to switch—but at the moment, it looks like the only people adopting them are users of older versions.

Chrome had another strong month, up 0.64 points to 11.57 percent. Safari saw gains too, up 0.25 points to 6.61 percent. Opera appears unchanged at 2.15 percent.

The resumption of Internet Explorer's slide shows that last month's upward adjustment was temporary. The statistics source we use—NetMarketshare from Net Applications—attempts to weigh the raw data the company collections to account for different levels of usage in different countries. Browser preferences show substantial geographic variation—for example, Firefox has a much higher proportion of market share in Europe than it does in the US, and Internet Explorer is particularly strong in China and South Korea.

Sometimes the underlying causes for these variations seem clear; between 1999 and mid-2010, South Korea mandated the use of an Internet Explorer plug-in for online commerce (instead of relying on standard HTTPS), with the result that anybody performing online banking and purchasing had to use Microsoft's browser. Other browsers may have benefited from having particularly good localizations or text entry, especially for non-Latin scripts. But other preferences are harder to fathom; while Internet Explorer, and particularly Internet Explorer 6, is enormously widely used in China (both in the form of the standard browser, and value-added front-ends such as Maxthon), but beyond some feeling of domestic loyalty (Maxthon, among others, is developed in China), there's no obvious reason for this state of affairs. Some have blamed software piracy—pirated copies of Windows XP won't automatically install Internet Explorer 7 or 8—but even this explanation cannot tell the whole story. It doesn't explain the lack of penetration of Firefox, for example.

Whatever the reasons, these geographic variations are substantial. China alone accounts for just under a quarter of the Internet's user base, so even if Internet Explorer were used nowhere else, it would still achieve around a 23 percent market share. However, the websites that companies like Net Applications monitor rarely have equal appeal to users from around the globe, and so the statistics they collect tend to be skewed towards certain countries. Visits to Ars, for example, over-represent the US (60 percent of Ars users, but only 12 percent of Web users), and under-represent China (less than one percent of Ars users, and 23 percent of Web users). To correct for this skew, Net Applications scales its reported numbers so that they are representative of the entire Internet-using population.

While browser usage numbers are collected continuously, reports on the number of Internet users as a whole, and number of users within each country, are adjusted much less frequently. Last month was one of those adjustment months; Net Applications increased the weight given to Chinese browser preferences, to account for the fact that Chinese Internet users made up a larger proportion of the total. This in turn saw Internet Explorer's global share go up.

In spite of that one-off correction, however, Internet Explorer continues to slide. As strong as it may be in the China, users elsewhere are defecting to other options in their droves, and the increased weighting given to China appears to have done little to stabilize its share.

New version impact

When looking at the level of usage of individual versions, the influence of the new browsers is clearer. Internet Explorer 8 posted a loss for the first time, dropping 0.54 points to 34.41 percent. Firefox 3.6 similarly fell, from 17.82 percent in February to 17.18 in March. Microsoft was quick to boast of Internet Explorer 9's 2.5 million downloads in its first 24 hours—a number quickly eclipsed by Firefox 4, which garnered 7.1 million in its first day. These download numbers have translated into shares of 1.04 percent for the Microsoft browser, and 1.68 percent for the Mozilla one.

While downloading—and autoupdating—are clearly the only way that Firefox and Chrome users will get their browsers of choice, Internet Explorer is heavily dependent on Windows Update for distribution. Internet Explorer 9 is now available through Windows Update, but only to users with the beta or the release candidate installed. Broad roll-out won't occur until late June. If Mozilla's development plans work out as the group hopes, Firefox 5 should be nearing readiness by the time Internet Explorer 9 is given mass availability.

Older, worse versions of Internet Explorer continued their decline. Internet Explorer 7 dropped 0.18 points to 7.87 percent, and version 6 dropped 0.36 points to 10.97 percent. Both browsers are approaching a usage level that will justify their abandonment by site developers, and those with a predominantly European focus can probably cut loose the decade-old Internet Explorer 6 with impunity. Those catering to a Far Eastern audience unfortunately have no such luxury.

As always at Ars, the browsing preferences of our readership fly in the face of convention. Firefox and Internet Explorer are down (by 0.95 and 0.65 points, respectively), in spite of their strong new versions; Chrome is up a little (by 0.29 points), and Safari has surged by over a point (up 1.26 percent).