<!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="width=400,height=400,initial-scale=1.0">
  <style>
    div {
      position: fixed;
      background-color: blue;
    }
  </style>
</head>

<body style="width: 500px; height: 500px">
  <div id="bottom-fixed" style="left: 0px; bottom: 0px; width: 20px; height: 20px"></div>
  <div id="top-bottom-fixed" style="left: 0px; top: 0px; bottom: 0px; width: 20px"></div>
  <div id="right-fixed" style="top: 0px; right: 0px; width: 20px; height: 20px"></div>
  <div id="left-right-fixed" style="top: 0px; left: 0px; right: 0px; height: 20px"></div>
</body>
</html>