SYS-CON Media West Coast Bureau Chief Roger Strukhoff, reporting from Mountain View, CA, writes: Sunshine returned recently to Silicon Valley after two weeks of Seattle-like storms and overcast skies. Now comes news of fair weather for Mountain View-based Mozilla's Firefox browser, which is reportedly eating up as much as one percentage point per month of the browser market recently dominated by that dour giant from the grey Northwest.

After dispatching Netscape a few years back, if not the company's Navigator browser, Microsoft now faces a challenge similar to that posed by Linux in the operating systems space - a challenger following an open-source philosophy that is at odds with Microsoft's (and formerly Netscape's) purely capitalistic bent.

A new study released by San Diego-based WebSideStory states that Internet Explorer's market share dropped 1.5% (to 90.3%) in a six-week period from December through mid-January. Firefox, developed by open-source leader Mozilla now has 5% of the market, according to this study.

"People tell me I'm nuts to consider Firefox as being significant," one leading industry pundit told us privately. "Yeah, well Firefox does a great job, and you know, the browser has simply not improved since Microsoft (put Netscape out of business). Firefox will drive the new competitiveness and better products that Microsoft's defenders are always yammering about."

The WebSideStory report showed that other browsers have nipped another 2.1 percent of the market away from Redmond.

Mozilla promises better security with Firefox, an end to annoying pop-ups, "smarter" search, and RSS integration as ways to differentiate its browser from Internet Explorer. The company's Thunderbird e-mail product is designed to complement Firefox and provide shielding from spam. Mozilla also promises hassle-free downloading, which at least one reporter can confirm is a valid claim. Mozilla also says there are more than 120 extensions available for Firefox. (And it is also hawking T-shirts at its site, surely a sign that the product's has entered the realm of plausible acceptance.)

Launched late in 2004, Firefox has now been downloaded more than 19 million times, according to Mozilla. Whether it can continue to grow depends on its ability to read the vast majority of Web sites and whether it can survive what may be a fearsome marketing attack by the dominant company in the browser market.