The control panel uses the file /var/www/html/manager/index.htm to take you to the control panel login. (Thus the http://yourdomain.com/manager/ URL)   If Apache shows a directory listing or a forbidden error (forbidden error means the directory listings are disabled), when you go to http://yourdomain.com/manager , then you need to check a couple of things.

1. Most often, the problem is with the .htaccess file under /var/www/html.  This file can have a directive that tells Apache which index files to look for and it will apply to the html directory and to the manager subdirectory - affecting the control panel login.  If the .htaccess file exists and has a line using the DirectoryIndex directive, you need to make sure it includes the index.htm filename.

Example:  in the file /var/www/html/.htaccess, you need to have an entry like this:

DirectoryIndex  index.htm index.html index.php

2. Make sure the file /var/www/html/manager/index.htm actually exists.  If it is missing, contact support at 866 HardHat (866-427-3428) or open a support ticket at http://hardhathosting.com/helpdesk