Mozilla, which released the free 1.0 program in November, says an average of 250,000 people download Firefox every day and more than half a million Web sites feature Firefox promotions. The group promotes the program as an alternative to Microsoft's Internet Explorer, which has become a target for computer virus writers and other security exploits.

"What was just a small flame 100 days ago has since exploded into a phenomenal demonstration of the power of open source," lead Firefox architect Blake Ross wrote on a blog. "Tens of thousands of devoted users and fans are a powerful and capable force of change."

The Mozilla Foundation released on Thursday an update to the Firefox Web browser to fix several vulnerabilities, including one that would allow domain spoofing.

The open-source project released Firefox 1.0.1 to fix, among other bugs, a vulnerability in the Internationalized Domain Names (IDN), a standard for handling special character sets in domain names that lets companies register domain names that appear to be the same in different languages.

The band Wilco and its quiet, haunted leader, Jeff Tweedy, is something different. After its Warner label, Reprise, decided that the group's fourth album, Yankee Hotel Foxtrot, was no good, Wilco dumped them and released the tracks on the Internet. The label was wrong. The album was extraordinary, and a sold-out 30-city tour followed. This success convinced Nonesuch Records, another Warner label, to buy the rights back - reportedly at three times the original price. The Net thus helped make Wilco the success it has become. But once back in Warner's favor, many wondered: Would Wilco forget the Net?

We've begun to see the answer to this question. Wilco's Net-based experiments continue: the first live MPEG-4 webcast; a documentary about the band in part screened and funded via the Net; bonus songs and live recordings tied to CDs. Its latest album, A Ghost Is Born, was streamed in full across the Net three months before its commercial release. And when songs from it started appearing on file-sharing networks, the band didn't launch a war against its fans. Instead, Wilco fans raised more than $11,000 and donated it to the band's favorite charity. The album has been an extraordinary success - and was nominated for two Grammys.