renderer怎样给网址增加超链接

   <script type="text/javascript">

           function showUrl(value)
   {
   return ""+value+"";
   }
    
    Ext.onReady(function(){


            var data = [
   [1,'张三','男','20','www.baidu.com'],
   [2,'李四','男','21','www.gdqy.edu.cn'],
   [3,'王五','女','22','www.csdn.cn'],
   [4,'刘六','牛','18','www.youku.com']
];

var store = new Ext.data.SimpleStore({data:data,fields:["id","name","sex","age",'homepage']});

var colM = new Ext.grid.ColumnModel(
    [
    {header:"Id",dataIndex:"id",sortable:true},
    {header:"姓名",dataIndex:"name",sortable:true},
{header:"性别",dataIndex:"sex"},
{header:"年龄",dataIndex:"age",sortable:true},
{header:"地址",dataIndex:"homepage",renderer:showUrl}
]
);

var grid = new Ext.grid.GridPanel({
renderTo:"hello",
title:"706绿ddd色网吧",
width:700,
height:600,
cm:colM,
store:store,
autoExpandColumn:2

});
   });
  
  
    </script>
</head>

<body>
        <div id="hello"></div>
</body>

超链接无效 不知为什么

[code="java"]{header:"地址",dataIndex:"homepage",renderer:function(value,meta,record){
return String.format('{0}',value);
}} [/code]

[url]http://atian25.iteye.com/blog/414248[/url]