Firefox' share of the browser market has slipped for the first time since its introduction, according to NetApplications.com.

Over July, Internet Explorer - Microsoft's dominant browser - regained lost ground, growing from 86.6 percent in June to 87.2 percent. Firefox's share shrunk to 8.1 percent from 8.7 percent.

Over the course of this year, Firefox had posted monthly market share gains of between 0.5 percent and 1.0 percent at the expense of IE, according to NetApplications.com, which compiles its browser usage data from more than 40,000 websites monitored by its HitsLink.com service.

The results surprised NetApplications.com's COO Dan Shapero. While he didn't expect Firefox to gain on IE forever, he did expect that Firefox's market share would slow down before it shrunk.

However, Firefox's advances remain extremely impressive and at this point it's impossible to tell whether July's results are the beginning of downward trend or a one-time anomaly, Shapero said.

NetApplications.com has said in the past that reaching a 10 percent market share would be a milestone for Firefox which could help it win acceptance in the corporate market.

Apple's Safari ranked third and grew its share slightly to 2.13 percent from 1.93 percent, while Netscape, which once ruled this market, slid a bit to 1.50 percent from 1.55 percent. Opera came in fifth with a 0.49 percent market share.