if a website is behind a proxy, and this proxy decides to cache more pages than wished for, is it possible and sensible to use a meta tag to force the proxy to drop its cache and give a new version of a page?
I read that proxy's don't always read the html they are forwarding, so that sounds as if it's not a sensible idea. However, the proxy does not always listen to the server either, so using a refersh-command in the http-header may also fail.
Proxies normally don't parse meta tags in HTML files, but they do interpret and obey HTTP headers. HTTP headers are the command lines sent with every object (HTML file, image etc.) from the webserver to the browser before the real content is sent. A number of these headers influence caching. You can't send these headers from plain HTML files, but you can send them from scripting languages like PHP.