While the first stable W3C "Recommendation" for HTML5 is not expected until the end of 2014, certain features of the new standard can already be enjoyed, as long as users have the latest versions of their web browsers.
Yet, despite efforts of web developers to nudge users to update their browsers, including initiatives such as Browser Awareness Day, a reliably consistent and modern web experience will simply not be available to everyone in the foreseeable future.
One big reason is that developers are “stuck” with Internet Explorer 8. Typically, web developers watch browser usage statistics to determine when to drop older browsers from cross-browser considerations as new websites are designed and built. In that vein, IE7 is no longer supported by an ever-growing number of websites. But IE8 is different.
This is due to the fact that:
a) Users of Windows XP simply cannot upgrade their version of Internet Explorer beyond IE8, and
b) Windows XP was the number one operating system in the world until around the middle of 2012, only recently falling to roughly 33% of market share as XP slowly becomes supplanted by newer Microsoft products like Windows 8, which ships with IE10 installed.
Because Microsoft chose not to develop a version of IE9 (or 10) that would is compatible with Windows XP, this large group of users is forever limited to IE8, unless they adopt a competing browser like Chrome or Firefox. As such, web developers are likewise limited, even as IE8’s market share has dropped to a few points below ten percent and might otherwise be retired. The usual “please update your browser” will not suffice in this case.
While this does not mean developers must build sites only for IE8 and ignore all of the newer possibilities, considerations do have to be made throughout the development process for how a site will perform in IE8. IE8, therefore, will continue to demand developer time and resources until Windows XP becomes thoroughly obsolete.