Bizarre bug: in a PHP script that serves video files, I have a few test conditions (authenticate token, make sure file exists, etc.) before sending a \"video/mp4\" header an
Without the video/mp4 header, the server will send the default content type header, usually text/html, some browser may look at what's being served and ignore the MIME type.
Add error_reporting(E_ALL);to the beginning of the script, and use firebug or similar to examine the headers being sent.