Firefox's once-strong surge against Microsoft Internet Explorer is showing signs of losing momentum, a Web metrics firm said Wednesday.

San Diego-based WebSideStory released market share numbers for Firefox, IE, and other browsers that noted Firefox has crept up from April's 6.75 percent to September's 7.86 percent, a single percentage point gain in five months. During the first few months after its November, 2004, release, Firefox was adding another point each month.

"It looks like Firefox has hit the push-back point," said Geoff Johnston, an analyst with WebSideStory. "We always knew there was a finite number of early adopters out there and a finite number of Microsoft haters who would switch to something new, but we didn't know what that number was. It looks like we're approaching it."

Last year, there was talk among Mozilla Foundation executives of hitting 10 percent market share by the end of 2005. That's unlikely to happen.

"That was doable based on the initial trends," Johnston said, "if those trends had held up. They didn’t."

Internet Explorer's market share as of Friday, Sept. 23, said WebSideStory, was 88.46 percent, just a slight decrease from the 88.86 percent in late April. Much of Firefox's gains, in fact, have come not at IE's expense, but at that of non-Firefox browsers from the Mozilla code (including the Mozilla suite and the stand-alone Netscape), as well as browsers by others, such as Apple's Safari and Opera Software's Opera.

"For many, IE is just not broken," said Johnston in explaining the small dip in Internet Explorer.

"The really bad news isn't on IE, but on the other browsers," he added. "People like choices, it seems, but they don't like too many choices. Netscape and Opera are the most vulnerable to losing existing market share. Opera, for instance, now has to steal users from Firefox, not IE, since the pool of IE users willing to change has dried up.

Last week, Opera changed its licensing practices, and set its browser free. "I hate to say this, but Opera was a year or 18 months too late doing that," said Johnston.

Both IE and Firefox figure to release updates before the end of the year, Internet Explorer to a public beta for IE 7 on Windows XP, and Firefox to version 1.5. Neither, Johnston figures, will much move the numbers.

"I don't think that they'll make a big difference," he said. "Even if IE 7 is great, Firefox won't loose a lot of users. They're fiercely loyal."

But Firefox will find it difficult to move into the double digits of market share, and retain those numbers. "It's hard to get there," said Johnston. "To do it, Firefox has to go mainstream."

WebSideStory isn't the first Internet measurement vendor to highlight Firefox's slow down. In fact, rival NetApplications' August numbers showed a small decline in the Mozilla browser's share.