<html>
<head>
<script type="text/javascript">
function setFontSize()
{
document.getElementById("p1").style.fontSize="larger";
}
</script>
</head>
<body>
<p id="p1">This is an example paragraph.</p>
<input type="button" onclick="setFontSize()" value="Change font-size" />
</body>
</html>