To enable items cache in the client side only, you only need to have installed on your Apache server the mod_expires module. Once installed, specify a default cache for all elements accessed by our server is as easy as typing the following directive in the httpd configuration of our site (.htaccess or httpd.conf):
ExpiresActive On ExpiresDefault "access plus 1 month"
* One month expiration since the access for all elements.
Probably, a better directive for heavy web elements like images, CSS's and JS's based on the filetype: