Setup mod page speed on your server :

mod_pagespeed is an open-source Apache module that automatically optimises web pages and resources on them. It does this by rewriting the resources using filters that implement web performance best practices. Web masters and web developers can use mod_pagespeed to improve the performance of your web pages when serving content with the Apache HTTP Server.

mod_pagespeed includes several filter that optimise JavaScript, HTML and CSS stylesheets. It also includes filters for optimizing JPEG and PNG images. The filters are based on a set of best practices known to enhance web page performance. Webmasters who set up mod_pagespeed in addition to configuring proper caching and compression on your Apache distribution should expect to see an improvement in the loading time of the pages on your websites.