通常，在应用程序根文件夹中有多个Web.Config文件时，会发生这种情况. 只需检查您是否有多个.如果是这样，请删除重复的副本.

阅读此处解决的类似问题: ASP.NET 2.0& "allowDefinition =" MachineToApplication"错误消息 [ http://forums.asp.net/p/769696/769696.aspx [ ^ ]

Generally this happens when you have more than one Web.Config file in your application root folder.
Just check if you have more than one. If so, remove the duplicate copies.

Read a similar issue resolved here:ASP.NET 2.0 & "allowDefinition=''MachineToApplication''" error message[^]

Other useful link that has similar issue discussed: http://forums.asp.net/p/769696/769696.aspx[^]