ASP.NET母板页问题：为什么创建第二个母板页的时候出现这个错误？？

图片说明
第一个母板页代码

 <%@ Master Language="C#" AutoEventWireup="true" CodeFile="MasterPage.master.cs" Inherits="MasterPage" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>无标题页</title>
    <asp:ContentPlaceHolder id="head" runat="server">
    </asp:ContentPlaceHolder>
</head>
<body>
    <form id="form1" runat="server">
   <div style="height:50px;background-color:#CCCCCC;text-align:center">
   头
   </div>
    <asp:ContentPlaceHolder ID="ContentPlaceHolderBody" runat="server">
    </asp:ContentPlaceHolder>
   <div style="height:30px;background-color:#66CCFF; text-align:center">
   &copy;版权所有2010
   <br />
   脚
   </div>
    </form>
</body>
</html>

第二个母板页代码

 <%@ Master Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="false" CodeFile="MasterPage2.master.cs" Inherits="MasterPage2" %>

<asp:Content ID="content1" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="content2" ContentPlaceHolderID="ContentPlaceHolderBody" Runat="Server">
</asp:Content>

具体要看代码，或者参考

http://bbs.csdn.net/topics/390103421