Site Offline After Saving a Setting
This is a MySql error. MySQL is not getting fed the correct logon information. Can you logon to mysql using your drupal credentials - either by command line or PHPMyAdmin or some other method. If you can't logon it's a credentials problem. Otherwise it's likely a path problem.

In your settings.php file, make sure everything is correct. Double check it

$databases = array (
  'default' =&gt; 
  array (
    'default' =&gt; 
    array (
      'database' =&gt; 'MYDATABASENAME',
      'username' =&gt; 'MYUSERNAME',
      'password' =&gt; 'MYPASSWORD',
      'host' =&gt; 'localhost',
      'port' =&gt; '',
      'driver' =&gt; 'mysql',
      'prefix' =&gt; '',
    ),
  ),


);