YouTube begins HTML5 rollout

YouTube on Wednesday announced that it's finally going live with support for HTML5 video. HTML5 video is the Web standard that allows users of most modern-day browsers to play hosted videos in their browser without having to rely on Adobe's Flash player.
In order to use the new feature, users will need to opt in to the HTML5 program on TestTube, which is where the company houses a number of other experimental features.
The only browsers that are currently supported include Google Chrome, Apple's Safari, and Internet Explorer with the Chrome frame installed. Not included on the list are Opera or Mozilla's Firefox, despite the fact that recent versions of both browsers work with the HTML5 video spec.
Along with the browser limitations, watching YouTube videos in HTML5 mode requires that the videos being watched are free of ads, user-created captions and annotations.

source::cnet

p.s. you can experience youtube videos in <html5> format using this extension in google chrome browser - https://chrome.google.com/extensions/detail/kchoimdlcbapmcdnheaahjcdpdjdpfco

note -firefox and opera don't support <html5> format

hmm..