<!DOCTYPE html>
<html>
<head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <title>bug 1059167</title>
  <style type="text/css">
    body {
        width: 200px;
        height: 200px;
        border: 1px solid black;
    }

    .item {
        width: 100px;
        margin-left: 80px;
        padding: 1rem;
        background: red;
        box-sizing: border-box;
    }

    p {
        background: blue;
    }
  </style>
</head>
<body>
  <div class="item"><p>Content</p></div>
</body>
</html>