Ten years later, Windows XP still dominates the Web by Philip Elmer-DeWitt @FortuneMagazine January 1, 2012, 3:56 PM EDT E-mail Tweet Facebook Google Plus Linkedin Share icons And in the Apple market, Lion is still trailing two-year-old Snow Leopard Data: NetApplications. Graph: PED In its final monthly report for 2011, NetApplications offers a window on the shifting fates of the various flavors of Microsoft MSFT Windows and Mac OS X that show up at its 40,000 clients’ websites. As a rule, creaky old legacy systems dominate. Windows XP, which Microsoft introduced in August 2001, is still the single most-present PC operating system, with a 46.5% share of global Web traffic. And Mac OS X 10.6 (Snow Leopard), which Apple AAPL launched in Aug. 2009, still has a 3.1% market share to Lion’s 2.0% But despite the persistence of aging OSs, there was a lot of rapid movement in 2011. Lion’s Web presence went from 0% to 2% in just over two months. And Windows 7, for its part, went from 21.7% to 37% in the space of a year, a 71% increase. It was not a good year for Vista or “Other,” however. Both experienced significant share drops in 2011. For a summary of NetApplications methodology, see here.