your PHP server doesn’t have the MySQL module loaded or you can’t use mysql_(p)connect function

To add more to what Rob said, you should not be using the deprecated Server & Database panels in DW.  They were removed from DW CC for a reason.  The code is grossly outdated and incompatible with modern servers running the latest versions of PHP.

If you can't code manually with MySQLi (improved) or PDO, you can purchase commercial extensions to replace the deprecated panels in DW.

http://www.webassist.com/dreamweaver-extensions/mysqli

http://www.dmxzone.com/go/22096/updated-replacing-dreamweaver-server-behaviors-with-dmxzone-extensions/

Nancy O.

The mysql module is deprecated and you should use MySQLi or PDO for database connections.

You can verify which database connection methods are available by running php on your server. To do so, create a new PHP file, place in it the following code:

<?php

phpinfo();

name it info.php, and upload it to your server. Then run it. It will report which database connection methods are available.