The number of downloads of Firefox has topped 25 million, indicating that the open-source browser continues to make gains in the market dominated by Microsoft Corp.'s Internet Explorer.

Downloads of Firefox 1.0 had reached 25.24 million as of Friday, just over 100 days since its release, according to the Mozilla Foundation, developers of the browser. A preview release of Firefox 1.1 is scheduled for April.

Security concerns have been a major impetus for consumers to switch from IE to alternative browsers, with Firefox benefiting the most. As of January, IE's market share had fallen to 92.7 percent, while Firefox's share had risen to 4.8 percent, according to JupiterResearch, a division of Jupitermedia Corp. Other browsers, such as Netscape and Opera, accounted for the rest.

"Overall, they're gaining lots of attention," Robert Lerner, analyst for Current Analysis, said of Firefox. Nevertheless, the open-source browser is not expected to overtake Microsoft in the foreseeable future.

"That's not going to happen, but, over time, there may be pressure placed on Microsoft. (Firefox) is gathering steam and gaining traction," Lerner said.

Earlier this week, at the RSA Conference in San Francisco, Microsoft chairman and chief software architect Bill Gates announced that the company would update IE sooner than originally planned to improve security. Microsoft plans to begin beta testing IE 7.0 in early summer, rather than ship the upgrade with the next version of Windows, scheduled for release next year.

The challenge for Mozilla, as well as other organizations developing browsers, is to lure website developers into designing their applications for IE alternatives. Many websites today have been fine-tuned for IE.

"IE has been the defacto standard for a lot of years, and that's tough to get around," Lerner said. "People have been raised on IE, so it's tough to replace."

Nevertheless, there are signs that a browser war is imminent. America Online Inc., which competes with the Microsoft entertainment portal MSN, started beta testing a standalone browser this month. Search engine Ask Jeeves is talking to Mozilla developers about building its own branded browser on top of Firefox.

Google Inc., on the other hand, hasn't announced any plans for releasing a browser, but the search market leader has hired Firefox's lead engineer Ben Goodger and Mozilla developer Darin Fisher, who ran the cookies and permissions part of the non-profit's browser development efforts.

In a side note, a Firefox fan pointed out on Mozilla's marketing site, called Spread Firefox, that search for "browser" or "best browser" in either MSN search or Google brought back results in which the Mozilla Foundation homepage and the download site for Firefox were listed in the first two slots.