Vimeo embedded video cannot be played in Firefox

Question

Here is my config:
- Mac 10.9
- Firefox 28-29

My iframe containing the Vimeo video stays black and displays this error message:
< This video can't be played with your current setup. >
It works fine in all the other browsers.

Markup iframe:  
<iframe src="//player.vimeo.com/video/83913899?title=0&amp;byline=0&amp;portrait=0&amp;color=111" width="960" height="540" frameborder="0" allowfullscreen="0" kwframeid="1"></iframe>

Link to page:
http://www.monakimprojects.com/projects/uniqlo-campaign#slide-02

PS : A friend told me it works fine for Firefox 29, Mac OS X 10.6.
So it looks like it is an OSX problem.

Answer 1

Can't comment yet because of lack of reputation, but there's something I think is worth sharing.

Chrome and Firefox have disabled Flash across the board. Users would have to update or reinstall Flash. This makes it worse for the situation mentioned in this post. Not so much for Chrome since it plays without using Flash, but definitely a problem for Firefox on Mac, which users may not know an update is necessary to view the Vimeo video.

Google and Mozilla pull the plug on Adobe Flash: Tech giants disable the program on browsers following 'critical' security flaw