css background image cover center

CSS
html { 
  background: url(images/bg.jpg) no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}body {
  background-position: center;
  background-repeat: no-repeat;
  background-size: contain;
}
Source

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