Responsive Youtube video

HTML

<div class="embed-container">
  <iframe src="http://www.youtube.com/embed/4aQwT3n2c1Q" allowfullscreen="" frameborder="0"></iframe>
  </div>

CSS

.embed-container {
  position: relative;
  padding-bottom: 56.25%;
  padding-top: 30px;
  height: 0;
  overflow: hidden;
  max-width: 100%;
  height: auto;
}

.embed-container iframe,
.embed-container object,
.embed-container embed {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}