<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html><head>
  <style type="text/css">
	p { margin: 0px; }
        ul { border: 2px solid blue; }
	li { border: 5px solid transparent } /* prevent margin collapsing */
        .test1
          p
           { margin-bottom: 30px; }
        .test2
          p
           { margin-top: 30px; }
        .test3
          p
           { margin-top: 30px; margin-bottom: 30px; }
        .test4
          p
           { margin-top: 20px; margin-bottom: 10px; }
        .test5
          p
            { margin-top: -10px; margin-bottom: 10px; }
  </style>
</head>
<body>
<ul class="test1"><li><p>P (30px bottom margin)</p></li></ul>

<ul class="test2"><li><p>P (30px top margin)</p></li></ul>

<ul class="test3"><li><p>P (30px top+bottom margin)</p></li></ul>

<ul class="test4"><li><p>P (20px top and 10px bottom margin)</p></li></ul>

<ul class="test5"><li><p>P (-10px top and 10px bottom margin)</p></li></ul>
</body>
</html>