Microsoft's Internet Explorer 6 and 7 continued to see their shares of the U.S. browser market decline in May, according to data from analytics company StatCounter, even as pickup continues for the newer Internet Explorer 8. Although IE 6 and 7 were market-share stalwarts a year ago, both browser versions have seen their usage dwindle in thanks to IE 8 and rival browsers such as Google Chrome and Mozilla's Firefox.

In May 2009, according to StatCounter, IE 6 occupied about 11.47 percent of the market, while IE 7 had 43.45 percent and IE 8 had 8.5 percent.

In May 2010, the numbers showed radical change: IE 6 claimed 4.47 percent of the browser market, IE 7 had 16.64 percent and IE 8 had 30.49.

Some of Microsoft's newer competitors saw substantial gains during the period, with Firefox 3.6 rising to take a 19.85 percent market share. In StatCounter's reckoning, Google Chrome 4.0 occupies about 6.53 percent of the market and Safari 4.0 owns 8.46 percent.

The market declines for both IE 6 and 7 could easily reflect those browsers' increased age. Microsoft claims, in fact, that the market-share falls are by design. 

"The fall of both these versions was expected, and in fact we wish to accelerate," Ryan Gavin, senior director of Internet Explorer, said in a June 1 statement. "Internet Explorer 8 is encouraging more and more people to move off of Internet Explorer 6 onto a modern browser—meaning developers can spend more time innovating and less time replicating workarounds."

For some Websites, IE 8 needs a feature called Compatibility View to render all elements properly; Microsoft has been working to reduce the list of Websites that need that feature. As of March, only about 19 percent of high-traffic Websites rendered in IE 8 standards, a number the company seemed highly intent on increasing.

Microsoft previously pledged to continue support of IE 6 through April 2014, despite calls from some quarters to phase out the browser. In July 2009, a brief furor erupted after Digg, a content-sharing Website, said it would stop supporting IE 6 "soon," followed by destinations such as YouTube asking their users to upgrade.