Domino Web server does not log HTTP return code 401

Hi All Domino Web experts, please help.

My Domino Web server does not log login failure properly. For example, if I type in wrong password, it logs status code 304 (Not modified as expected), instead of 401 (Authentication Failure). My application uses custom login form. If I disable Session Authentication in the server document to make the application to use IE default login screen, then server catches 401 fine.

Any ideas why my server does not catch return code 401 when custom login form is used?

Any help would be greatly appreciated.

Thank you very much in advance.

Helen