Why does calling a web service or an HTTP handler produce two unauthorized errors, and then the only success?

Question

When accessing the application I wrote, FireBug shows that each call to the web service or HTTP handler is executed three times, and the first two times show as “401 unauthorized”, even if they return the correct result. It is consistent. Each challenge does the same.

Any ideas why this is happening?

Answer 1

NTLM permission negotiation is in progress. Check MSDN on Microsoft NTLM: http://msdn.microsoft.com/en-us/library/aa378749.aspx

Answer 2

( ) IIS, Windows.
NTLM ( Kerberos), NTLM.

Answer 3

Are you sure that calls returning 401 also return the correct result? They should not be.

It sounds like an agreement for authorization.