The recent skirmish between Apple and Adobe has focused attention on Flash vs. HTML5. Its native support for video could render flash obsolete. Furthermore, it treats audio and video as first class citizens, and this has widespread implications for how audio and video are integrated into web sites, e.g. imagine being able to insert an adsense like feed into a video that is playing without server side connections.
However, its impact is much broader, especially in th emobile ecosystem. HTML5 has several new APIs such as offline storage, local SQL database, drag and drop and geolocation. These will change how web sites are developed. For more details,
However, the most important change will be in the mobile ecosystem. HTML5 has the potential to reverse the trend towards mobile apps. Thorough its APIs, HTML5 enables most of the capabilities that mobile app. developers have come to depend upon without the challenges of developing/maintaining multiple apps (for theiPhone, Android, etc.).
The recent re-launch of the YouTube mobile site is a sign of the times. In many ways, it renders YouTube’s iPhone app obsolete. With better functionality for touchscreen users, it is more efficient, faster, has a better interface, allows for like/unlike flags and playlists, streams better quality video over 3G, and includes suggested searches.
For developers, this has obvious benefits. A mobile web site can be tweaked and enhanced faster than issuing updates for an onboard app which requires multiple versions and approvals by various hall monitors (such as the iTunes store). Also, most mobile browsers use webkit as their layout engine (see http://en.wikipedia.org/wiki/Comparison_of_layout_engines_(HTML5) making it easier for developers to build web apps that will work across devices. In addition, even where developers do need to build applications, HTML5 frameworks (such as Sencha) make it much easier for developers to produce cross platform applications
If HTML5 does reverse the trend towards platform specific mobile apps, it could level the playing field between various mobile OSs and under-cut Apple’s tightfisted control over its ecosystem. Yet another sign that Apple’s best days may be behind it…