The performance tab in the template parameters offers a selection of improvements to the speed and optimization your website.

 

Compress system and core CSS files: this option enables the compression of all CSS files that are loaded  by default into your site. Please note that this is not  include the CSS loaded within the child theme or the other CSS files that might be loaded by other joomla extensions.

Remove mootools from the Joomla output:  this option removes the loading of mootools  and the caption JavaScript from your site. Please note that while this will reduce the load time of your site you may still need to include these scripts in your site for the functioning of  third-party extensions.

 Combined core JavaScript  files: this option combines the JavaScript required for this super fish, panel menu and the Zen grid  hidden panel.  Please note  that this option overrides the subsequent script inclusion settings for the panel and super fish menu.

Remove Joomla  meta-tag generator:  By default Joomla  adds its own meta-tag to the output of your  website. While this setting tends to have no direct effect on your website performance it may be of help from a security perspective to remove this meta-tag to reduce the ability for hackers to identify your site as a site that uses the Joomla CMS.