The software giant said it expects use of the latest browser to increase as the company finishes developing additional localized versions and as Windows Vista is released to the general public later this month. Vista will ship with Internet Explorer 7 built in.

Tony Chor, an Internet Explorer group program manager at Microsoft, wrote in a blog posting that even more important than the current number of installations is the adoption rate. "We expect the numbers to continue to climb steadily," Chor wrote.

Browsing the Market

According to Web analytics outfit WebSideStory, over 25 percent of all visitors to sites in the U.S. now use Internet Explorer 7, coming in second to IE 6, which claims 62 percent.

WebSideStory expects IE 7 to become the dominant browser inside a year, gaining ground as Microsoft continues to roll it out through its Windows Update services.

IE 6 hit 80 percent market share in early 2004, before reaching a high of 89 percent on March 8, 2006, according to WebSideStory. Launched in August 2001, IE 6 grew to a share of more than 45 percent in a single year on Windows operating systems, then surpassed IE 5 shortly thereafter.

All versions of Internet Explorer, grouped together, claim between 85 percent and 90 percent of the worldwide browser market, according to measurements from several analytics firms.

Changing One for the Other

The new IE 7 figures don't necessarily mean Redmond is gaining in the browser market. Rand Schulman, chief marketing officer at WebSideStory, said the new browser is simply being swapped out for older editions and hasn't had an impact on other browsers.

"We expect IE 7 to have little short-term impact on Firefox because once a favorite browser gets installed, it's difficult to replace," he said in a published statement. "IE 7 will grow quickly, but directly at the expense of IE 6."

Firefox, a popular browser among techies, is used by roughly 11 percent of U.S. Web surfers. Firefox's latest version has continued to gain market share, reaching about 4 percent last month.

Schulman said that both browsers "appear to be taking market share from their predecessors as the overall market share of each browser (all versions) has remained fairly stable."