<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>"this line should have a green background" lime margin offset</title>
    <style type="text/css">
      .a { background: lime; margin: 0; height: 1em; }
      .b { margin: -1em 0 0 0; }
    </style>
  </head>
  <body>
    <div class="a"></div>
    <div class="b">This line should have a green background.</div>
  </body>
</html>