CTRL+F5 Cache release

Hi again.
Looking for the best way to solve the CTRL+F5 issue for old visitors when ever i change the website.
I've found some solutions on the web like this one
<?php
header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past
?>

but there's always poor information what it does and how it works, and not to forgett that someone always claims that there's a better way to do it.
Also where i should include the code so it work properly?

Or is it better to use .htaccess to force cache release?

Bump this sucker up :)
Same problem but with a clean html site.

I have a div that i upload some picture to now and then.
All new picture won't show up untill i press ctrl+f5.

I've tried with

<meta http-equiv="expires" content="wed, 09 aug 2000 08:21:57 gmt" />
<meta http-equiv="cache-control" content="no-cache" />
<meta http-equiv="pragma" content="no-cache" />


and
<img src="images/pic.jpg?34523576"/>

But non of them works.
It's been over 24 hours since i uploaded them and still no new picture.

Any other solution on the problem? If possible, refresh the div once right after you enter the site?