<!DOCTYPE html>
<html>
<head>
  <style>
    body {
      -webkit-animation-name: throb;
      -webkit-animation-iteration-count: infinite;
      -webkit-animation-duration: 2s;
      -webkit-animation-timing-function: ease-in-out;
    }

    @-webkit-keyframes throb {
      0% { background-color: #fff; }
      50% { background-color: #000; }
      100% { background-color: #fff; }
    }
  </style>
</head>
<body>
</body>
</html>