And the HTML code looks like this:
...
<style>
  body {
    margin:9px 9px 0 9px;
    padding:0;
    background:#FFF;}
  #level0 {
    background:#FC0;}
  #level1 {
    margin-left:143px;
    padding-left:9px;
    background:#FFF;}
  #level2 {
    background:#FFF3AC;}
  #level3 {
    margin-right:143px;
    padding-right:9px;
    background:#FFF;}
  #main {
    background:#CCC;}
</style>
...
<body>
  <div id="level0">
    <div id="level1">
      <div id="level2">
        <div id="level3">
          <div id="main">
            The code you are reading.
          </div>
        </div>
      </div>
    </div>
  </div>
</body>
...