javascript中的没有权限问题，代理非常间单

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>无标题页</title>
<script language="javascript" type="text/javascript">
// <!CDATA[
        function Button1_onclick() 
        {
            var obj = document.getElementById("Menu");
            var str;
            for (i=0; i<obj.childNodes.length; i++)
            {
                str = i+"<br>";
                document.write(str);
            }
        }
     // ]]>
</script>
</head>
<body>
    <form id="form1" runat="server" >
    <div id="Menu" class="MenuShadow" style="height:118px;width:108px;Top:50px;Left:50px;">
    <div class="MenuRight" style="background-color:MintCream;">
    <div id="0" class="MenuItem" >
    <span class="MenuItemText">第0项</span>
    </div>
    <div id="1" class="MenuItem" >
    <span class="MenuItemText">第1项</span>
    </div>
    </div>
    </div>
    <input id="Button1" type="button" value="button" onclick="return Button1_onclick()" />    </form>
</body>
</html>