Fully responsive HTML5 video

Use width and max-height on the <video> element:

/*CSS*/ 
video {
  width: 100%;
  max-height: 100%;
}

<!-- HTML -->

<div id="player-overlay">
  <video>
    <source src="../static/video/10s.mp4" />
    <source src="../static/video/10s.webm" type='video/webm; codecs="vp8, vorbis"' />
    <source src="../static/video/10s.ogv" type='video/ogg; codecs="theora, vorbis"' />
  </video>    
</div>

 Run code snippetExpand snippet

http://jsfiddle.net/fHG69/

Also, you’re missing a semicolon after background-color. When absolutely positioning an element to fill the screen, I prefer to set top, bottom, left, and right instead of setting height and width.