HTML5 is a set of the latest and greatest features of the web. However, as a web developer, it isn’t really viable to make a site which uses these features without proper browser support. Because HTML 5 is a big vague, let’s check which percentage of browsers support CSS3:
|Mobile / tablet|
The 66.49% is even a pessimistic estimation as BlackBerry OS 6+ support CSS3 and modern Symbian phones support it too.
This means that mobile browsers are more likely to support CSS3 than desktop browsers. This could be explained that most people surf the web with the default browser installed on their device, and people buy a new phone more often than they buy a new desktop.
Old mobile browsers
When we look at the percentage of potential bad browsers, there is Symbian (4.70%), Proprietary or Undetectable (0.37%), ACCESS NetFront (0.28%) and Obigo (0.11%). This adds up to 5.46%. However, Symbian browsers have improved a lot over the last couple of years, so the percentage of really bad mobile browsers is most likely a lot less than 5.46% and this figure will decline even further in the future.
I’d say that creating a mobile website today is completely different than before or what W3C still lets us believe. Instead of avoiding PNG’s, using CSS3 makes more sense. However, you’ll still need to add fallbacks or make sure it looks good without it.