Firefox 36 (Desktop and Mobile) is now available on the beta channel.
The release notes are published on the Mozilla website:
This version introduces many new HTML5/CSS features, in particular the Media Source Extensions (MSE) API which allow native HTML5 playback on YouTube. The new preferences implementation is also enabled for the first half of the beta cycle, please help us to test this new feature!
On the mobile version of Firefox, we are also shipping the new Tablet user interface!
Download this new version:
And as usual, please report any issues.