The web servers are installed with a RAM cache to help speed up your website.
The caching software will serve static objects from cache with a 60 minute timeout and dynamic objects with a 20 second timeout before rechecking the website. This means if you are actively updating the site, you may not see the changes straight away.
As such, during active development you may wish to temporarily disable the server's caching software software. This can be done by adding the following anywhere in your website's main .htaccess file:
Header set no-cache "1"
Header set Set-Cookie "NO_CACHE=1; path=/;"