Vaya ritmo, me lo bajo y lo instalo en el HDD.
Yo a Firefox le fuerzo a usar html5 en Youtube con
Greasemonkey +
YouTubeCenterEste ultimo...
Add the old black background to the player.
Add country flags to the comments.
Change the color of the rating bar.
Turn the lights off.
Animate the thumbnails.
Rating and video quality on thumbnails.
Ability to resize the player to your liking.
Remove all advertisements from YouTube.
Remove the play icon in the title.
Repeat the video you're watching.
Grid view for subscriptions and collection.
Choose to enable or disable DASH playback.
Force the player to be either flash or HTML5.
Remove the endscreen.
Prevent the player from auto-playing videos.
Download YouTube videos.
and many more...Salu2