​x
 
<html>
<head>
<script type="text/javascript">
function changeList()
{
document.getElementById("ul1").style.listStyle="decimal inside";
}
</script>
</head>
<body>
​
<ul id="ul1">
  <li>Coffee</li>
  <li>Tea</li>
  <li>Water</li>
  <li>Soda</li>
</ul>
​
<input type="button" onclick="changeList()" value="Change list style" />
​
</body>
</html>
​