Also note that websites are embedding HTML5 video in newer browsers, so need another method to stop those from auto-play. You may want to add the Firefox extension
Flashblock which reportedly also stops HTML5 based video from auto-playing.
In fact, some websites take marketing videos to another annoying level by not just auto-playing, but disabling controls to stop it? I've discovered it can be done easily as in the example below. Click the
video to play.
Now, try stopping the top HTML5 video? Surprisingly, the player controls are actually not disabled, and is identical to the video below it. Yet the top video was placed one-layer below(z-index) on the page. Akin to placing a piece of glass on top of an object or photo. You can see it but not actually touch it, as in the player controls in this instance.
BTW, you can use this example to test whether your browser extensions stops the top video from auto-playing?