<html>
<head>
<script type="text/javascript" src='http://code.jquery.com/jquery-1.5.2.js'></script>
<script type="text/javascript">
$(document).ready(function(){
$("p").click(function () {
$(this).toggleClass("blue");
});
});
</script>
</head>
<style>
.blue { color:blue; }
</style>
<body>
<p class=blue>A</p>
</body>
</html>