HTML5 Video Autoplay not working correctly

Question

Im using this code:

Answer 1

html {
  padding: 20px 0;
  background-color: #efefef;
}

body {
  width: 400px;
  padding: 40px;
  margin: 0 auto;
  background: #fff;
  box-shadow: 1px 1px 5px rgba(0, 0, 0, 0.5);
}

video {
  width: 400px;
  display: block;
}