publish a website and uplaod to my server

Question

hi,
    am created simple website and publis it. then published folder was make it as virtual directory, and finally upload to my ftp server but its getting following error

server error in '/' application

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 44:             ASP.NET to identify an incoming user. 
Line 45:         -->
Line 46: 		<authentication mode="Windows"/>
Line 47: 		<!--
Line 48:             The <customErrors> section enables configuration 

please help me