为什么不行？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
</head>
<body>
<ul id="test"><li>JavaScript</li><li>HTML</li></ul>
<script type="text/javascript">
var otest = document.getElementById("test");
var ot = document.createElement("li")
ot.innerHTML="This is a f**k"
insertBefore(ot,otest);
</script>
</body>
</html>
