The Firefox web browser has been causing a commotion among users and snaring snippets of market share from Microsoft's Internet Explorer since June, long before Version 1.0 of the open-source software was officially released in November.

But statistics suggest that corporate users aren't the major group fueling the growth of Firefox. The new browser's most dramatic spikes in usage are on weekends, according to Chris Hoffman, director of engineering at the not-for-profit Mozilla Foundation, which developed Firefox. This suggests it is home users that are enjoying the free benefits of Firefox, rather than businesses.

That observation was borne out by an email poll of IT managers conducted recently by Computerworld magazine in the USA. Only two of the 25 respondents said their organisations have standardised on Firefox. Another 11 said they have tried Firefox or use it on a personal basis. But 17 said that their companies have no current plans to re-evaluate their decisions to go with Internet Explorer.

"We've been standardised on Microsoft Internet Explorer for as long as we've had a standard," says Patricia Coffey, an assistant vice president in IT at Allstate Insurance in Northbrook, Illinois. "Basically, we run Microsoft on the desktop as our standard, so we use IE, Office, Outlook and so on."

Allstate's "big gripe . . . is the security issues with Microsoft," Coffey says. But she adds that the insurer is content with IE from a features standpoint.

Security is the very reason why Jefferson County in Colorado ordered its 2000 government workers to switch to Firefox about five months ago, says David Gallaher, the county's director of IT development. Gallaher says he came to view IE as "a VDS – a virus distribution system."

"It's hazardous to your corporate health," says Gallaher. "You have to turn off everything that makes Internet Explorer interesting just to avoid the impact of the viruses. Even Microsoft employees have told us, 'You should turn off ActiveX controls.' "

Jefferson County ran the beta version of Firefox and is moving to Version 1.0. Gallaher says the migration has gone well, except for components in a few applications that don't yet support Firefox, including the county's enterprise document management system. But he says the application vendors have indicated that they will fix the problems.

One alluring feature in Firefox is a tabbed browsing capability, which Internet Explorer lacks. Tabbed browsing allows users to load pages from multiple sites without having to open a new browser window for each one. The tabs make it easier to switch back and forth between the sites.

The feature is "real handy," says Gallaher, adding, "What has Microsoft done with IE for the last few years? They've ignored it."

Gary Schare, a director of product management at Microsoft, disputes that assertion. He claims that Microsoft continues to make major investments in Internet Explorer, including significant security enhancements that were part of Windows XP Service Pack 2. Schare adds that Microsoft partners and independent software vendors are developing add-ons for IE and even complete browsers with tabbed browsing capabilities built on top of it.

Carroll Pleasant, a systems associate at Eastman Chemical in Kingsport, Tennessee, says his company is sticking with Internet Explorer as its standard browser. "Nothing else is practical for us," he says. "We have a significant number of internal systems that are dependent on IE."

Ping also plans to continue using Internet Explorer, says David Chacon, a technical services manager at the Phoenix-based maker of golf equipment. But Firefox "has really raised the bar on functionality and usability," Chacon says. "I hope Microsoft is taking notes."