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.video-wrapper {
	position: relative;
	padding-bottom: 56.25%;
	padding-top: 25px;
	height: 0;
  iframe {
  	position: absolute;
  	top: 0;
  	left: 0;
  	width: 100%;
  	height: 100%;
  }
}

<div class="video-wrapper">
  <iframe width="560" height="349" src="http://www.youtube.com/embed/n_dZNLr2cME?rel=0&hd=1" frameborder="0" allowfullscreen></iframe>
</div>