The browser wars are back on in earnest. For the second time in three months, Internet Explorer made large gains, picking up almost 1 point of market share. Chrome, Firefox, and Safari all lost out, as Internet Explorer 9 won over new users.

Internet Explorer gained 0.99 points for a 53.88 percent market share, taking it to a six month high. Firefox is down 0.37 points to 20.55 percent. This is the lowest share the browser has been at since October 2008. Chrome is down a third of a point to 18.57 percent, Safari is down 0.17 points to 5.07 percent, and Opera also fell, dropping 0.09 points to 1.62 percent.

This is a strong performance from Microsoft, though it may come as a surprise to many. In mid-March, Web analytics firm StatCounter announced that Chrome had overtaken Internet Explorer for the first time ever: on Sunday March 18th, for one day only, Chrome was the number one browser. This seems at odds with Internet Explorer's growth and Chrome's decline.

StatCounter, however, is recording something slightly different from Net Marketshare, the numbers we use for our monthly look at the browser war. StatCounter measures raw unadulterated pageviews. It doesn't attempt to make any corrections for pre-rendering (Chrome will render pages ahead of time if it thinks that the user will look at them, boosting its number of pageviews), it doesn't attempt to count unique visitors, and it doesn't attempt to use geographical weighting to account for uneven visitor demographics (some sites are more popular in the US than China, for example, so their browser usage will tend to be more representative of American users than Chinese ones).

StatCounter's numbers are still interesting as a measure of Web usage, but Net Marketshare's numbers, which do try to account for things like the geographical variation, are a better measure of browser market share—that is, the number of people using each browser.

A look at the version breakdowns for each browser reveals how Microsoft has made these gains.

Internet Explorer 9 has picked up 2.6 points of share in the last month. This is its strongest month since its release. Internet Explorer 8 fell by almost the same amount, dropping by 2.19 points. Internet Explorer 7 dropped a fraction, down 0.09 points, and Internet Explorer 6 picked up 0.66 points.

The numbers suggest that Internet Explorer 8 users are switching to Internet Explorer 9 in relatively large numbers, particularly on Windows 7: 34.5 percent of Windows 7 users are using Internet Explorer 9.

Microsoft has been vigorously promoting Internet Explorer 9, most recently with a campaign that encourages nerds to give Internet Explorer a second chance; the latest part in a broader campaign to educate users and explain to them that Internet Explorer 9 really isn't the same as the much-hated Internet Explorer 6.

On top of that, the company is continuing to use automatic updates to move Internet Explorer 7 and 8 users onto the latest version.

Together, these factors seem to be driving upgrades to the current browser version, and users are actually sticking with it rather than switching to other options.

Chrome's update story is the same as ever. Its automatic update process is reliable, consistent, and effective, keeping the large majority of Chrome users on the latest and greatest version of the browser.

Firefox continues to have a large number of users on version 3.6 and below. The final update for 3.6, version 3.6.28, was released on March 13th. Unless there's a security emergency, there will not be a 3.6.29: support for 3.6 ends on April 24th. Firefox users wanting a browser with long-term support but without six-weekly major updates will have to switch to Firefox Extended Support Release 10.0.4. Everyone else should switch to the current main branch, which on April 24th will be Firefox 12.

Mozilla plans to make Firefox 3.6 offer an update to version 12 once the end of its supported lifecycle has been reached. This means that Firefox 3.6 users should start to decline. However, as with the die-hard group of Firefox 3.5-and-below users that still exists, it's unlikely that they will all opt to do so.

Automatic, silent updates are still being developed for Firefox. The latest 32-bit nightly builds (version 14) include automatic updates that do not show any UAC prompts on Windows. They're not yet silent updates, though this too is planned. Until these things are finished, the browser will struggle to have transitions as smooth as Chrome's.

In mobile, iOS users continue to outnumber Android users, with the surprising implication that Android users don't actually use the Web very much on their smartphones.

At Ars, however, Chrome and Android are dominant.