<!DOCTYPE html>
<html>
<head>
  <style type="text/css">
    .box {
      width: 10px;
      height: 10px;
    }
    .scrollable {
      overflow: scroll;
    }
    .out-of-flow {
      position: absolute;
    }
    .big {
      margin: 200px;
    }
  </style>
</head>

<body>
  <div class="scrollable box">
    <span class="big">Scrolling content</span>
    <div class="out-of-flow box">Out-of-flow content.</div>
  </div>
</body>
</html>