You want to decrease page load time and eliminate unnecessary hits on your web server.
Employ caching mechanisms to indicate to browsers in that web
pages, images, and other site elements can be displayed from locally
saved versions, and that must be refreshed from a newer version on the
server. With Apache's
module, you can control caching by file type and directory. PHP's
header( ) function and HTML
<meta> tags provide caching
control for individual pages.
Cached files can speed the display of a web page. But lacking an expiration date for cached resources, a browser must still send a request to the server to check the validity of each file needed to render a page. Even when the server agrees that a file can be loaded from the cache, rather than downloading it again, the roundtrip between browser and server unnecessarily delays the page's load time and demands extra server processing cycles to complete. When the web server sends an explicit expiration time for each file, caching can eliminate the request-and-response routine the browser would otherwise need to validate its cache.
sets an expiration date for a resource and sends it to the browser in
Expires http response header
for each request. The
header is a date and time after which a site file should not be
cached. If you have access to your Apache configuration file
(typically, httpd.conf) you can check to see if