Microsoft Corp.'s share of the U.S. browser market has slipped below 90 percent as the Firefox browser continues to grow in popularity, according to independent tracking by WebSideStory.
Firefox, an open-source browser collectively developed by the Internet community under the Mozilla Foundation, had a 6.8 percent share as of April 29, an increase from 3.0 percent since WebSideStory began tracking Firefox separately in October.
Other browsers based on the Mozilla code, including America Online Inc.'s Netscape, had a 2.2 percent share, while Microsoft's Internet Explorer share was 89 percent, a drop from 95 percent in June.
The figures are for all operating systems combined. On computers running Microsoft's Windows, Internet Explorer has a 91 percent share, down from 97 percent in June.
Outside the United States, Germany is among the leading adopters of Firefox, with a 23 percent share, compared with 69 percent for Internet Explorer.
"They just seem to be averse to Microsoft products and really interested relatively in these open-source products,'' said Geoff Johnston, a WebSideStory analyst.
Microsoft is strong in Asia, with Internet Explorer commanding a share of 94 percent in Japan and 98 percent in China.