Database connection error!

A connection to the Database could not be established.
Please check your username, password, database name and host.
Also make sure config.php is rightly configured!

Notice: Use of undefined constant X_SADMIN - assumed 'X_SADMIN' in /var/www/html/forums/db/mysql.php on line 136

Warning: mysql_error(): supplied argument is not a valid MySQL-Link resource in /var/www/html/forums/db/mysql.php on line 143

Warning: mysql_error(): supplied argument is not a valid MySQL-Link resource in /var/www/html/forums/db/mysql.php on line 144

MySQL encountered the following error: (errno = )

In the following query: