asp.net – 无法识别配置文件Web.config

我和我的朋友在Asp.Net中实现了一个应用程序,我有一个奇怪的问题.
我从ftp服务器下载了最新的源代码(我们还没有安装源代码控制工具),当我尝试编译并运行应用程序时,IIS抛出异常.我检查了目录,并且有一个web.config文件.
我不明白有什么不对:(.感谢您的帮助:).
这是什么IIS响应：

Runtime Error
Description: An application error occurred on the server. The current custom error 
settings forthis application prevent the details of the application error from being 
viewed remotely (for security reasons). It could, however, be viewed by browsers 
running on the local server machine.

Details: To enable the details of this specific error message to be viewable on 
      remote machines, please create a <customErrors> tag within a "web.config" 
      configuration file located in the root directory of the current web 
       application. This <customErrors> tag should then have its "mode" 
       attribute set to "Off".


<!-- Web.Config Configuration File -->

<configuration>
    <system.web>
        <customErrors mode="Off"/>
    </system.web>
</configuration>


Notes: The current error page you are seeing can be replaced by a custom error page 
by modifying the "defaultRedirect" attribute of the application's <customErrors> 
configuration  tag to point to a custom error page URL.


<!-- Web.Config Configuration File -->

<configuration>
    <system.web>
        <customErrors mode="RemoteOnly" defaultRedirect="mycustompage.htm"/>
    </system.web>
</configuration>

天啊！！！我找到了问题.我没有检查Windows资源管理器选项’显示所有已知的文件扩展’和我保存web.config与txt扩展,我没有看到这个荒谬的错误.谢谢你的帮助！