HTML: force proxy server to fetch new copy of page

I know this is a duplicate question, but I've tried:

<META HTTP-EQUIV="CACHE-CONTROL" CONTENT="NO-CACHE"> 
<META HTTP-EQUIV="EXPIRES" CONTENT="-1">
<meta http-equiv="pragma" content="no-cache" />

And yet I still sometimes get cached pages. (old开发者_如何学Python data etc.)

And this is the solution I've always seen when searching stackoverflow for a sollution.

You should send the cache-control headers with the HTTP protocol. The proxy you are using may not parse HTML for meta tags.

Cache-Control: no-cache