Server Error in '/web' Application.
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Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level. This error can be caused by a virtual directory not being configured as an application in IIS.

好像下载的所有的源码都是错在这一句：
Line 43: <authentication mode="Windows" />

Source File: F:\web\dotnet\guestbook2\web.config Line: 43


是不是我还有哪儿没有设置啊？？？能教教吗？