Some of the common SPNego related questions surrounding errors and warnings.
For Firefox, type about:config
make the "network.negotiate-auth.delegation-uris" value empty.
The krb5.conf file is not found or configured.
- Look for your settings such as the system property "java.security.krb5.conf" is pointing to the right krb5.conf file (Server Side)
- Export environment variable KRB5_CONFIG should point to the krb5.conf file for Client side login.