<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
<style type="text/css">
.message{
display:block;
width:200px;
height:100px;
background-color:#CCC;}
</style>
</head>
<body>
<script type="text/javascript">
main=document.body;
var newnode=document.createElement("p");
p.className="message";
var textnode=document.createTextNode("I love JavaScript!");
newnode.appendChild(textnode);
main.appendChild(newnode);
p.className="message"; 改成：newnode.className="message";