There are a lot of cookies running in Joomla for tracking, hit counting, statistics, etc., that are slowing the site, upload the server, and upset the users.
There is a way to disable all these cookies for visitors, keeping the usual options, including the front end login. Follow these stages:
Disable the statistics of the site, by stopping the mosvisitor cookie, from Global configuration > Statistics > Statistics: No
Disable the Template Chooser module to stop the jos_user_template cookie.
Take a look to the components to see the ones that start their own PHP sessions. Try do avoid these sessions.
Delete the comment out (//) from line 697 of /includes/joomla.php:
// setcookie( $sessionCookieName, '-', false, '/' );
Due to the set of POST/GET parameter namely “force_session”, set in standard login module, there will be anyway a user session for log in. If you use a different module for log in, add this parameter.
Note: You can comment out the line 25 in /offline.php: // session_start(); It seems that this is a reminiscence of the old versions, and there is no need to start a PHP session in this file, as Joomla uses its own session way.