​x
 
<html>
<head>
<script type="text/javascript">
function changeMargin()
{
document.getElementById("p1").style.margin="100px";
}
</script>
</head>
<body>
​
<input type="button" onclick="changeMargin()" value="Change margins of a paragraph" />
​
<p id="p1">This is a paragraph</p>
​
</body>
</html>
​