High page speed and short page load times of your website are essential for good search engine rankings today. In this FAQ, I will show you how to enable caching of graphic and CSS files in apache on Ubuntu and Debian.
The first step is to enable the expires module in apache:
a2enmod headers expires
This module allows the apache web server to set HTTP headers, in this case, to set the modification header for static assets like image and CSS files that don't change often.
Add the following config snippet inside the vhost file of the web site or at the end of the file /etc/apache2/apache2.conf to enable it globally.
<FilesMatch "\.(ico|pdf|flv|jpg|jpeg|png|gif|js|css|swf)$"> Header set Cache-Control "max-age=3024000, public" </FilesMatch>
Finally reload apache to apply the configuration change.
service apache2 reload
On ISPConfig 3 servers, the snippet can be added in the "Apache Directives" field of the website instead. There is no apache reload required as ISPConfig takes care about that.