problem during Add Web reference to Application

hi,
i am going to add web service in my application but there is an error at the time of Add WEB Reference. the Error is given

The document at the url http://****/VinserveWebService/service.asmx was not recognized as a known document type.
The error message from each known type may help you fix the problem:
- Report from 'http://****/VinserveWebService/service.asmx' is 'The document format is not recognized (the content type is 'text/html; charset=utf-8').'.
- Report from 'DISCO Document' is 'There was an error downloading 'http://****/VinserveWebService/service.asmx?disco'.'.
- The request failed with HTTP status 403: Forbidden



so please give me solution for this Problem.

thanks.