If you’ve used Google Page Speed then you’ve probably seen “Leverage browser caching” as one of the items on the Medium Priority list. And it’s a real simple fix if you’re running Apache. Just create or edit your .htaccess file for the site you want to enable it on and input the following.
<IfModule mod_expires.c> ExpiresActive on ExpiresByType image/gif "access plus 1 years" ExpiresByType image/jpeg "access plus 1 years" ExpiresByType image/png "access plus 1 years" ExpiresByType text/css "access plus 1 years" ExpiresByType text/js "access plus 1 years" ExpiresByType text/javascript "access plus 1 years" ExpiresByType application/javascript "access plus 1 years" ExpiresByType application/x-javascript "access plus 1 years" #ExpiresDefault "access plus 1 days" </IfModule>
And Viola, you’re now telling Web Browsers not to grab Images/CSS or Javascript unless otherwise required.