Many new websites are relying on features that only modern browsers can offer. Web developers constantly have to battle with the many users that don't regularly upgrade their browsers (by choice, because they're ignorant, or because their IT departments won't let them). This hinders the progress of the Web as it slowly moves towards the latest and greatest features browser technologies, like HTML5. That being said, a surprisingly large number of users (71 percent) already run the latest official versions of their browser, according to the latest data from Pingdom and StatCounter.
Google is leading the pack for browser vendors, thanks to Chrome's built-in update feature. 90.6 percent of all Chrome users have the latest stable release (version 7). Furthermore, considering Chrome's fast release cycle, it's very likely that many of the users not on version 7.0 are actually using a later build (either version 8 or version 9). Following Chrome, the next three are Firefox (81 percent are on version 3.6), Opera (77 percent use version 10.6), and Safari (71 percent run version 5.0).
It's not very surprising that Internet Explorer is dead last. Many haven't upgraded to the latest version of Microsoft's browser, though it's still impressive to see that 60.2 percent of IE users are running version 8. IE8 is actually the most popular browser, even if you don't take version numbers into account for other browsers. Furthermore, many are eagerly giving Internet Explorer 9 a shot.
Now the question is, are you running the latest stable or beta version of your browser?