<html>
<head>
<script src="https://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("p").bind("mouseover mouseout",function(){
$("p").toggleClass("intro");
});
});
</script>
<style type="text/css">
.intro
{
font-size:150%;
color:red;
}
</style>
</head>
<body>
<p>Hover the mouse pointer over this paragraph.</p>
</body>
</html>