Whenever anybody visits a Website, they leave behind a calling card stating what browser and operating system they're running. Net Applications takes these statistics from 40,000 sites in order to measure OS popularity.

Linux isn't stealing the market share. In fact, the figures show the Linux market share held mostly steady during 2009-2010, at between 0.9 and 1.1 percent, after rising steadily from 0.65 percent in November 2007 (no doubt down to the rise in popularity of Ubuntu). So, sadly, .

Macs are providing a stronger challenge to Windows, with a share of 3.43 percent in November 2007 growing steadily to 5.02 percent at the end of 2010. In other words, five in every 100 computers right now runs Mac OS X--although the Mac share might be even higher, bearing in mind some Mac owners run Windows.

However, the biggest market share thief is mobile devices, in the form of cellphones and tablets, which have seen the fastest growth. iOS, Apple's mobile phone OS , grew from 0.24 percent in January 2009, to 1.69 percent in December 2010, and Java Mobile Edition--which powers the browsers in many mobile phones--grew from 0.22 percent to 0.91 percent in the same period

If these trends continue then the future will be a pluralistic computing universe, in which users demand the freedom to work on many different types of computing device. The desktop PC running Windows won't decline in importance; it'll just have to share the stage.