Per cortesia mi aiutate a capire come risolvo questo errore che mi sembra di capire dipenda dalla mancata connessione al mio database mysql.

Potete vedere l'errore qui:

http://lnx.sinapsi.org/piwigo/

Warning: mysqli::mysqli(): (HY000/2000): mysqlnd cannot connect to MySQL 4.1+ using the old insecure authentication. Please use an administration tool to reset your password with the command SET PASSWORD = PASSWORD('your_existing_password'). This will store a new, and more secure, hash value in mysql.user. If this user is used in other scripts executed by PHP 5.2 or earlier you might need to remove the old-passwords flag from your my.cnf file in /web/htdocs/www.sinapsi.org/home/piwigo/include/dblayer/functions_mysqli.inc.php on line 67

Warning: my_error(): Couldn't fetch mysqli in /web/htdocs/www.sinapsi.org/home/piwigo/include/dblayer/functions_mysqli.inc.php on line 824

Warning: my_error(): Couldn't fetch mysqli in /web/htdocs/www.sinapsi.org/home/piwigo/include/dblayer/functions_mysqli.inc.php on line 824
Piwigo encountered a non recoverable error

[mysql error ]
Can't connect to server

#1    my_error /web/htdocs/www.sinapsi.org/home/piwigo/include/common.inc.php(121)
#2    include_once /web/htdocs/www.sinapsi.org/home/piwigo/index.php(26)