The U.S. browser usage market share of Firefox grew from 3.03 percent to 4.06 percent in the one-month period from Nov. 5, 2004 to Dec. 3, 2004.

The U.S. browser usage share of Firefox, the Mozilla-based browser, has grown by more than a third over the past month, according to the latest independent study from WebSideStory, a provider of on-demand Web analytics.

In the one-month period from November 5, 2004 to December 3, 2004, Firefox's online usage share grew from 3.03 percent to 4.06 percent. This compares to a gain of 13 percent during the previous month, from October 8 to November 5.

"Firefox's gains are clearly accelerating," said Rand Schulman, WebSideStory's chief marketing officer. "Much of it has to do with the release of Firefox's version 1.0 on November 9, after several months of offering a preview version. Firefox's stated goal of gaining 10 percent of the market over the next year no longer seems unattainable."

According to WebSideStory, Firefox has made significant gains and Microsoft's Internet Explorer's usage share continues to fall in the United States. Between Nov. 5 and Dec. 3, Internet Explorer's share dropped 1.09 percentage points to 91.80 percent, according to WebSideStory. This compares with a 0.32 percentage point drop the previous month. Since June 4, 2004, when IE's usage share first began to drop due to security concerns, IE has lost a total of 3.68 percentage points.