<!DOCTYPE html>

<html>
<head>
  <style type="text/css" media="screen">
    body { background-color:silver }
    .box {
        height: 200px;
        width: 200px;
        margin: 10px;
        padding: 5px;
        background-color: blue;
        overflow:hidden;
    }
  </style>
</head>
<body>
    <div id="iframe-content" class="box">
      <iframe src="composited-subframe.html"></iframe>
    </div>
</body>
</html>