Firefox continues to chip away at Internet Explorer's market share, with Microsoft's browser posting its largest loss last month since November 2008.

Of course, we're still talking about small numbers overall. IE fell 1.1 percentage points to 66.6 percent in August, so it's in no immediate danger of yielding to Firefox, the main beneficiary who gained 0.8 percentage points to 23.3 percent. But the downward trend has to be cause for concern for Microsoft. In the past 12 months, IE has unwillingly given up 8.6 points of browser share.

On a positive note (for Microsoft), IE8 gained 2.7 percentage points in August, more than making up for IE6's 2.4 percentage loss, which is the biggest drop since December 2007. IE7 also took a step backwards, however, to the tune of 1.9 points.

While Firefox and IE duke it out for the top spot, Chrome is on pace to replace Safari as the No. 3 browser in 11 months. And if Google's aggressive campaign to promote Chrome pays off, we could be looking at a 3-way slug fest for the most used browser on the planet.