Visitors to your website will experience faster page loads if you take some steps to enable caching of static content, such as CSS files, javascript and images. One simple way to enable such caching is to use mod_expires with Apache. If you run your own server you can easily enable this module. If you are on a shared host you should check with your hosting provider to see if its enabled. If you are looking for reasonably priced virtual private hosting you should checkout rimuhosting.com.

Here is the official documentation for the module.

I found that with ExpiresByType specifying text/javascript did not set the expiration time for javascript files. However, changing text/javascript to application/javascript did work.

If you are serving dynamic content do not set a default expires time (ie with ExpiresDefault). You do not want to cache dynamic pages like a shopping cart or other dynamically generated HTML.