<!DOCTYPE html>
<!--
 | If the element has "position: absolute", the containing block is established
 | by the padding edge of the nearest ancestor with a "position" of "absolute".
 |   http://www.w3.org/TR/CSS21/visudet.html#containing-block-details
 -->
<html>
<head>
  <style>
    body {
      margin: 0px;
    }
    .absolutely-positioned {
      position: absolute;
    }
    .level-1 {
      background-color: #b3e5fc;
      padding: 10px;
    }
    .level-2 {
      background-color: #40c4ff;
      padding: 20px;
    }
    .level-3 {
      background-color: #00b0ff;
      padding: 30px;
    }
    .level-4 {
      background-color: #01579b;
      height: 60px;
      width: 60px;
    }
    .topleft {
      left: 100%;
      top: 100%;
      width: 25%;
      height: 25%;
    }
  </style>
</head>
<body>
  <div class="absolutely-positioned level-1">
    <div class="level-2">
      <div class="level-3">
        <div class="absolutely-positioned topleft level-4"></div>
    </div>
    </div>
  </div>
</body>
</html>