I found those very interesting articles to understand KERBEROS, it includes also other web resources:

https://msdn.microsoft.com/en-us/library/cc246080.aspx

http://blogs.msdn.com/b/friis/archive/2009/12/31/things-to-check-when-kerberos-authentication-fails-using-iis-ie.aspx?Redirected=true

http://jorgequestforknowledge.wordpress.com/2012/01/26/troubleshooting-authentication-problems-kerberos-or-ntlm/

http://blogs.technet.com/b/askds/archive/2008/03/06/kerberos-for-the-busy-admin.aspx

http://setspn.blogspot.fr/2010/06/kerberos-basic-troubleshooting-tip-1.html

http://www.windowsitpro.com/article/kerberos/Kerberos-in-Active-Directory-125786

http://www.windowsitpro.com/article/kerberos/Kerberos-Delegation-and-Troubleshooting-128831

http://blogs.technet.com/b/askds/archive/2008/05/14/troubleshooting-kerberos-authentication-problems-name-resolution-issues.aspx

http://setspn.blogspot.fr/p/kerberos.html

http://jorgequestforknowledge.wordpress.com/2010/10/12/user-principal-names-in-ad-part-1/

http://jorgequestforknowledge.wordpress.com/2010/10/12/user-principal-names-in-ad-part-2/

http://jorgequestforknowledge.wordpress.com/2010/10/12/user-principal-names-in-ad-part-2/

Kerberos Authentication tester (tool): http://blog.michelbarneveld.nl/michel/archive/2009/12/05/kerberos-authentication-tester.aspx

Kerberos error codes: http://retrohack.com/kerberos-response-codes/

Kerberos protocol registry entries and KDC configuration keys in Windows : http://support.microsoft.com/default.aspx?scid=kb;EN-US;837361

Apache and Kerberos authentication: http://pix-mania.dyndns.org/mediawiki/index.php/Apache_-_tutoriels_-_authentification#avec_Internet_Explorer