Linux held steady, sticking at about 0.96%. But Apple's iOS rose from 0.23% in February 2009 to 1.69% in December 2010. Android only accounts for 0.40% of operating systems but is on the upswing. Java ME quadrupled share from 0.23% to 0.91% in the past two years.

Microsoft has also long dominated the browser market because most Windows users surf the Web with Internet Explorer, the OS's built-in browser. But the rise of viable alternatives such as Mozilla's Firefox and Google Chrome has eaten into Microsoft's browser share as well.

Internet Explorer share dropped from 69.72% in January 2009 to 57.08% in December 2010, according to Net Applications data, with Firefox holding steady in the 22% range and Chrome rocketing up from 1.52% to 9.98%.

StatCounter's figures show even more depressing news for Microsoft on the browser front. StatCounter has Internet Explorer usage dropping to 46.94% in December, with more than half of all Web browsing now taking place on Firefox, Chrome and the Mac's Safari.

While Net Applications tracks only unique visitors, StatCounter's numbers compile all the hits across a network of 3 million websites. One possible explanation for the difference between Net Applications and StatCounter browsing data is that the most active Web users choose Firefox and Chrome instead of Internet Explorer. In that scenario, most computer users would surf the Web with Internet Explorer, but the majority of total browsing would occur on non-Microsoft browsers. But further research is probably necessary to make that determination.