Says the WSJ. .09% doesn't sound like much, until you consider that, a) There are approximately 1.25 billion Internet users worldwide and b) Companies have been making mobile devices that run Windows since 1996, and they make up only .06% of web traffic.
By the way, if you don't have an iPhone but find yourself envious of the neat browsing features that allow it to cope with having a screen smaller than what most webpages were designed for, check out Opera Mini. It's an alternative browser for your non-iPhone that basically allows you to do the same thing. It won't magically turn your phone's screen into a touchscreen, but it will make it much more comfortable to browse normal websites from your phone. You can download it by visiting operamini.com from your phone's browser.