<!DOCTYPE html>
<!--
 | A stacking context and a containing block may be different boxes,
 | so the parent stacking context should offset the child stacking context
 | by the sum of all offsets of containing blocks between it and the child.
 -->
<html>
<head>
  <style>
    .absolutely-positioned {
      position: absolute;
    }
    .level-1 {
      background-color: #b3e5fc;
      padding: 10px;
    }
    .level-2 {
      background-color: #40c4ff;
      padding: 20px;
    }
    .level-3 {
      background-color: #00b0ff;
      padding: 40px;
    }
    .level-4 {
      background-color: #0091ea;
      height: 100px;
      width: 100px;
    }
    .absolutely-positioned.level-4 {
      background-color: #01579b;
    }
    .with-z-index {
      z-index: -1;
    }
  </style>
</head>
<body>
  <div class="absolutely-positioned level-1 with-z-index">
    <div class="level-2">
      <div class="absolutely-positioned level-3">
        <div class="level-4"></div>
        <div class="absolutely-positioned level-4 with-z-index"></div>
      </div>
    </div>
  </div>
</body>
</html>