Chrome's share of the browser market is fading as users who abandoned Internet Explorer and Firefox start to return, an Internet measurement company said Tuesday.

At the end of its third week of availability, Google's Chrome accounted for 0.77 percent of the browsers that visited the 40,000 sites tracked by Net Applications, down from a 0.85 percent share the week before.

"The trend line on Chrome still has a slight downward angle, and these weekly numbers reflect that," said Vince Vizzaccaro, Net Applications' executive vice president of marketing. Although Chrome popped above 1 percent within hours of its release, the new browser now reaches that mark only in the middle of the night, US time, Vizzaccaro added.

Chrome's numbers, like those of Mozilla's Firefox and Apple's Safari, typically climb after work hours and then fall as work resumes the next day. Many businesses standardize on Microsoft Corp.'s Internet Explorer (IE) and don't allow employees to use alternate browsers.

IE and Firefox still showed share erosion compared to the period immediately before Chrome's September debut, but both browsers regained users last week, Vizzaccaro said. IE picked up 0.24 percentage points last week, while Firefox regained 0.06 points. Both, however, remained down for the month, as was Opera Software's Opera and AOL's now-defunct Netscape.

Apple's Safari, the only browser to escape Chrome's impact, was still on the plus side for September, ending last week up 0.45 percentage points from before Chrome, although the was down from the prior week's 0.68-point net gain.

Last week, Vizzaccaro said Safari's immunity could be traced to the lack of Chrome competition. Although Google has promised a native Mac OS X edition, its browser is currently only available for Windows XP and Windows Vista.

Computerworld's site metrics echoed Net Applications' trend for Chrome. The percentage of visitors to Computerworld.com who used Google's browser dropped to 4.01 points last week, down from 4.96 points.

Chrome's slow slide may be due to Google's low-key promotion, Vizzaccaro said. "The only marketing effort I've seen from Google is in sponsored links on search results for 'browser' or 'browsers' search terms," he said. "On Google, Chrome is naturally the top sponsored link. On Yahoo, it was second. And on Windows Live, I couldn't even find it in the first five pages of organic results."