If your site uses a secure connection(https), it is very important that all connected files (for example, video) are connected via https too. If you use one of MP4, WebM, OGG players, and including a video by Video URL with a third-party resource that does not support https, then you can see errors in the console of your site.
Solution
To avoid the error, remove the protocol from the link to the video: http://yoursite.com/video.mp4
