What problem is this (regarding Authentication Mode)?

[exshige]

Server Error in '/' Application.
----------------------------------------------------------------------------
----

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.

Source Error:

Line 30: "Forms", "Passport" and "None"
Line 31: -->
Line 32: <authentication mode="Windows" />
Line 33:
Line 34: