Vimeo does not offer HTML5 webM, only H.264. Vimeo's video pages
notice TenFourFox has no Flash Player then display an error message
about it: "This video can't be played with your current setup.
Please switch to a browser that provides native H.264 support or
install Adobe Flash Player."
I hope you tried StopTube before it stopped working (yesterday
or the day before) because of a YouTube change. Sorry, there's no
working alternative right now. Waiting for an updated version of
Edit: StopTube was updated to 0.2.1 today, so the developer seems
to be quick. It's working again and also looking better.
I tried StopTue after it stopped working and then forgot about
it -- no YouTube on TenFourFox for two weeks, I had to use Safari
with ClickToPlugin extension. Just noticed StopTube works again.
Thanks for the note!