New research shows the growth rate of open-source browser Firefox is slowing, while Microsoft's browser market share continues to dip.

Two tracking surveys released Monday showed that Microsoft's Internet Explorer Web browser has dipped below 90 percent market share.

IE, which comes preinstalled on the vast majority of computers, had already dipped below the 90 percent threshold in a November survey by OneStat, a Dutch Web metrics firm. At the time, Microsoft pointed to WebSideStory's results, which showed it was still above 90 percent.

With Monday's reports, WebSideStory's data indicated that IE had indeed dipped a hair below that psychologically important marker and was used to access surveyed sites 89.9 percent of the time.

Firefox, the Mozilla Foundation's open-source browser, has put Microsoft on the defensive by garnering nearly 27 million downloads since its November final release. Microsoft this month reversed itself and said it would release IE 7 with the next update of Windows XP. Previously, the company had said upgrades to IE would come only as part of the next major version of Windows, code-named Longhorn.

Read the entire story at CNET News.