Content Delivery Networks (CDN) have great benefits for optimizing your Joomla websites and for Google higher ranking due to website increased speed. You can use a CDN component/plugin to integrate a Content Delivery Network (CDN) in Joomla.

Incorporating a CDN with your website gives you several benefits, including the following:

Faster Page Loads - Since most of your files will be served from a much closer location to your end-users, the speed in which your page loads will be greatly increased.
Reduced Server Load - Since most of your files are no longer served by your own host, your server will be freed up to perform the basic tasks required of it.
Handle More Visitors - Because of the improvements just mentioned and other factors, your website will be able to handle the strain of a much larger user base that it could otherwise.
Higher SEO Rankings - Caused by the increase in performance to your site, something Google recently claimed effects SEO rankings.

Integrating your website and a CDN (like MaxCDN or Amazon CloudFront) with this plug-in is incredibly easy! This tutorial gives you the simple process involved with this integration.

Download the “CDN For Joomla!” plugin from download page.
Log into your Joomla Administrator Panel, hover over “Extensions” and click “Extension Manager.” Next to the “Upload Package File” box, click “Browse”, select the downloaded plugin file, and click “Upload & Install.”
After the installation is complete, go back to “Extensions”, click “Plugin Manager”, then find and click on “System – CDN for Joomla!” Click on it to setup the plugin.

Leave the “Site Root” value alone, type your CDN URL (e.g. http://foo.bar.netdna-cdn.com) into “CDN Domain”, then click “Save & Close.”

All done! You are now officially using our CDN service. You can check if your URLs are being rewritten to CDN URLs by loading the page and viewing the source code of the page.

Source: https://www.todhost.com/knowledgebase/707/How-to-setup-CDN-for-Joomla.html