【before】
<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").before("<b>Hello</b>");
});
</script>
</head>
<body>
<b>b</b>
<p>p</p>
</body>
</html>
