关于Ext显示的格式问题！

最近在学习Ext，在网上下载了"掏钱学ExtJS"，跟他上面的代码一样，但是显示却大相径庭...
代码如下：<html>    <head>        <meta http-equiv="Content-Type" content="text/html; charset=gbk">        <title>grid</title>        <link rel="stylesheet" type="text/css" href="../../resources/css/ext-all.css" />        <script type="text/javascript" src="../../adapter/ext/ext-base.js"></script>        <script type="text/javascript" src="../../ext-all.js"></script>        <script type="text/javascript">Ext.onReady(function(){    var cm = new Ext.grid.ColumnModel([        {header:'编号',dataIndex:'id'},        {header:'名称',dataIndex:'name'},        {header:'描述',dataIndex:'descn'}    ]);    var data = [        ['1','name1','descn1'],        ['2','name2','descn2'],        ['3','name3','descn3'],        ['4','name4','descn4'],        ['5','name5','descn5']    ];    var ds = new Ext.data.Store({        proxy: new Ext.data.MemoryProxy(data),        reader: new Ext.data.ArrayReader({}, [            {name: 'id'},            {name: 'name'},            {name: 'descn'}        ])    });    ds.load();    var grid = new Ext.grid.GridPanel({        el: 'grid',        ds: ds,        cm: cm    });    grid.render();});        </script>    </head>    <body>        <script type="text/javascript" src="../examples.js"></script>        <div id="grid"></div>    </body></html>
例子运行的是正常如下：
但是我自己的却是如下：为什么只是显示一行，末尾还有个下拉按钮