server error when accessing webservice

[miirpf]

when i tried to access a simple webservice from a client program
written in c#, i got the following error :

Server Error in '/Application14' Application.
--------------------------------------------------------------------------------

The request failed with HTTP status 401: Unauthorized.

Description: An unhandled exception occurred during the execution of
the current web request. Please review the stack trace for more
information about the error and where it originated in the code.

Exception Details: System.Net.WebException: The request failed with
HTTP status 401: Unauthorized.

can someone please tell me the remedy of this problem?
thanks in advance..
-miirpf