Microsoft's Bing search engine lost market share for the first time since its launch in May and its Internet Explorer browser continued its long, slow slide.

A turnaround could be in the offing: Windows 7 launches on October 22, and Microsoft's considerable marketing muscle may generate some lift beyond the operating system market.

But in the calm before the ad blitz, Microsoft's search and browser power is suffering.

Bing lost 0.2 percentage points, dropping to a 3.39% share of the global search market, according to NetApplictions. Google lost a similar number of percentage points, dropping to 83.13% global search share. Yahoo lost 0.44 percentage points to end up at 6.84%.

A different metrics firm, StatCounter, said that Bing declined slightly on a global basis, from 3.58% to 3.25%, a drop mirrored by Yahoo, which fell from 4.84% to 4.37%.

Globally, StatCount saw Google gaining rather than slipping, as NetApplications did: Google's global search share increased to 90.54% in September, from 89.57% in August, according to StatCounter's yardstick.

StatCounter's figures also show Google US search share rising to 80.08% in September from 77.83% in August.

Bing's share of the US search market in September dropped to 8.51% from 9.64% in August, according to StatCounter. Yahoo's US search share during this period dropped from 10.5% to 9.4%.

With regard to Web browser usage, Internet Explorer went from 58.69% in August to 58.37% in September, as StatCounter reports. According to NetApplications, Internet Explorer's decline went from 66.97% to 65.71%.

Firefox reached a global market share of 23.75%, according to NetApplications, a level just below its 23.84% high-water mark in April. Google's Chrome browser and Apple's Safari browser also posted gains to end up at 3.17% and 4.24% respectively.

As StatCounter sees it, Chrome actually passed Safari in August and increased its lead in September. Chrome finished the month with global market share of 3.69% while Safari came in at 3.28%.

InformationWeek has published an in-depth report on why businesses shouldn't shrug off Google's upcoming Chrome OS. Download the report here (registration required).