I use Moodle 2.6.1
In the settings "Media embedding" I checked the "HTML5 Video" and unchecked "Quicktime Player".
That means that if you embed a MP4-file somewhere in the text editor, Moodle uses the HTML5 <video> tag and the browser plays that video at the embeded place.
When I use Firefox (Version 26) Moodle does't use the <video>-tag, instead you have a normal link to the file.
Internet Explorer and Chrome work OK.
Doe's anyone has an idea why this happens with Firefox?