Almost two years to the week after AOL (NYSE:AOL) announced it would end support for Netscape's pioneering Netscape Navigator browser, which Microsoft (NASDAQ:MSFT) destroyed when it created its rival Internet Explorer (IE), new data suggests that IE is still losing market share, primarily to the open-source Firefox browser.

StatCounter, an analytics firm, says that Firefox's share of the browser market now stands at 32.06%, up almost seven percentage points from last November. Internet Explorer's share fell more than 12 percentage points over the same period.

Firefox isn't the only winner here. Apple's (NASDAQ:AAPL) Safari made modest gains, and Google's (NASDAQ:GOOG) Chrome browser gained almost as much as Firefox did -- up to 5.34% from 0.93% last November.

Blame it on Steve
We don't know precisely why IE is losing share, but Macs could be part of the problem. Apple has gained share from smaller PC market rivals this year, and it's putting pressure on leaders Dell (NASDAQ:DELL) and Hewlett-Packard (NYSE:HPQ) in the process. Macs don't use IE. They haven't for years. Each user that switches from PC to Mac also switches from IE to ... something else.

Serious Mac addicts will tell you that Safari is the platform's best browser. It certainly performs well enough on my aging MacBook Pro. But it also isn't my primary choice. Firefox is, because it's both browser and platform. Using Greasemonkey's scripts, I've tricked out the Firefox version of Gmail to the point where it has become a tool, rather than a chore. Call it cloud computing at its most functional.

Safari doesn't dabble in plug-ins and extensions the way that Firefox does. IE offers plug-ins for Windows, but users apparently have more interest in alternatives. IE's market share would be stable or growing if this weren't true.

Microsoft investors have reason to worry. This is a war, and it's being fought in the browser. The most functional environment for cloud computing will win this conflict. Going by the trend in the numbers, users increasingly believe that's Firefox.

But this is also Round 1 of a multiround bout. Get up off the mat, Mr. Softy. Internet Explorer needs you at your fighting best.

Have a different view? Let's hear it. You can weigh in using the comments box below.

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Fool contributor Tim Beyers had stock and options positions in Apple and a stock position in Google at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Twitter as @milehighfool. The Motley Fool is also on Twitter as @TheMotleyFool. The Fool's disclosure policy is up waaaaaay too early.