Firefox Entering The MainstreamFirefox Entering The Mainstream

Firefox is gradually moving into the mainstream in the United States, as the open-source newcomer approaches 10 percent of the browser market, mostly at the expense of Microsoft's Internet Explorer, a website monitoring firm said Friday.

The Mozilla Foundation's Firefox reached 8 percent of the market by the end of May, up from 7.38 percent in April, NetApplications, based in Aliso Viejo, Calif., reported. Since October, Firefox has gained between .5 to 1 percent each month, while IE has dropped.

Other web metrics suppliers have also reported steady growth, but some say they are seeing Firefox adoption slow a bit, following the spurt in the first few months after the 1.0 release in November.

Nevertheless, once the browser grabs 10 percent of the market, then it becomes mainstream and no longer a technology only used by Mozilla and open-source software fans or the anything-but-Microsoft crowd.

"When you hit 10 percent market share, you start to crossover from diehard Firefox users to a broader percentage of the market," Dan Shapero, chief operating officer of NetApplications, said. "It means there's others besides Mozilla fans adopting Firefox."

If one considers Microsoft customers "mainstream" consumers, not just technology buffs, then Firefox's gains are telling, Shapero said.

"They're clearly tapping into Microsoft's base," he said.

While Firefox gained in May, IE's market share fell .77 percent from April to 87.23 percent. Most other browsers saw little change in May, with the exception of Safari, which gained a modest tenth of a percent to 1.91 percent, according to NetApplications, which monitors traffic at more than 40,000 websites.

Market share numbers for IE and Firefox, however, vary substantially among web metrics firms. At the end of April, the latest numbers available, Firefox had 6.75 percent of the U.S. market, according to WebSideStory. Amsterdam-based OneStat pegged the number at 8.7 percent.

The French firm XiTi reported that Firefox had a 14 percent share in the U.S. and 14.1 percent in Europe at the end of May.