nothing like that

I can run it on multiple desktops without issue



just the thing is all the same program will be stacked together on taskbar
and if you close other Desktops, all program from the closed Desktop will be made available on main Desktop

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Firefox is using HTML5 to render youtube for a while now. (actually youtube will automatically use html5 for browser without flash for those videos that supports it)
the version im using for this test is Firefox 32.0.3 (latest as of now)

we are seeing the slow death of flash

http://www.youtube.com/html5