<!DOCTYPE html>
<html>
<head>
  <title></title>
  <style type="text/css" media="screen">

      div {
          width: 100px;
          height: 100px;
          background-color: black;
          animation: move 1s infinite;
      }

      @keyframes move {
          50% { margin-left: 60px; }
      }

  </style>
</head>
<body>

<div></div>

</body>
</html>