I am getting error when running web app which are downloaded from sites which is very similar to the error SUPERHUMAN got,that is

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: by Microsoft that offers a single logon and core profile services for member sites.Line 45: -->Line 46: <authentication mode="Windows"/> Line 47: <!-- AUTHORIZATION Line 48: This section sets the authorization policies of the application. You can allow or deny access


But when try to start IIS it is not responding properly I mean I can't see any default web site there .But the application which I am developing running properly (I am using VS2005).
What caused the error?Kindly help me out a solution for this....