That's because your site is secure. Browsers have started blocking insecure elements loaded on secure pages. The easiest solution is to remove the "http:" from the src of the iframe:
<iframe src="//player.vimeo.com/video/19513284?byline=0&portrait=0&color=ffffff" width="350" height="192" frameborder="0" webkitAllowFullScreen mozallowfullscreen allowFullScreen></iframe>
That will load via the proper protocol where necessary. Note that we are still working on getting our video files loading over https, but the embed will still work in the meantime (you'll just see a warning in the address bar in some browsers).