CSS: Responsive embed video trick

responsive-embed-video.html

<style type="text/css">
  .video-container {
    position: relative;
    padding-bottom: 56.25%;
    padding-top: 30px; height: 0; overflow: hidden;
}
 
.video-container iframe,
.video-container object,
.video-container embed {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}
</style>

<div class="video-container">
  <iframe src="http://www.youtube.com/embed/dFVxGRekRSg" frameborder="0" width="560" height="315"></iframe>
</div>