I sent Wolfram the information too. It looks like they have sent this information to their developers for a fix. Until then, I recommend using Chrome. Hope this helps. And thanks again Pieter!
Hello Michael McCain,
Thank you for contacting Wolfram Technical Support.
I see from your Wolfram Community post ( http://community.wolfram.com/groups/-/m/t/410913?p_p_auth=f1Eb8bFV ) that there is an issue with the code only when using Mathematica Online on the Safari web browser. It does seem that video embedding is not behaving properly in this case and I have forwarded an incident report to our developers with the information you provided.
We are always interested in improving Wolfram products and services and I want to thank you for bringing this issue to our attention.
Please don't hesitate to contact us, if you run into any other behavior problems.
Wolfram Technology Engineer
Wolfram Research, Inc.