Despite the release of Microsoft Internet Explorer 8 two weeks ago, Microsoft continues to lose browser market share to Mozilla's Firefox.

According to the latest data from Net Applications, the global market share for all versions of Internet Explorer slipped from 67.44% in February to 66.82% in March.

Firefox's global market share meanwhile rose from 21.77% to 22.05% during the same period.

Google (NSDQ: GOOG)'s Chrome browser and Apple's Safari browser also showed small gains, the former rising from 1.15% to 1.23% and the latter rising from 8.02% to 8.23% from February through March.

While relatively small shifts in market share may be attributable to data collection errors, Net Application's March statistics continue a longstanding downward trend for Internet Explorer, one that Microsoft presumably hopes to reverse with IE8.

IE8 has been doing fairly well, having risen from a market share of 1.26% on March 2 to 3.07% on March 31.

Those figures are based on Net Applications' hourly tracking numbers for IE8. The company's monthly numbers show IE at 1.17% at the end of February and 1.83% at the end of March.

Perhaps just as significant as Internet Explorer's continuing slide is the inability of Google's Chrome browser to make significant gains. With IE8 already more widely used than Chrome, which has been available for about six months, it's clear that Google will have to engage in more aggressive promotion if it wants to build a significant user base for its browser.

Chrome may become more appealing once its plug-in architecture matures -- there are a lot of potential users for whom the inability to use AdBlock Plus with Chrome is a deal breaker.

Given that Microsoft can expect significant gains for IE8 when Windows 7 finally ships, Google may have to put a link to Chrome on its home page and leave it there for quite a while to match Microsoft's distribution advantage.