The new version Internet Explorer 7 has a problem in caching of the displayed specially if you are using some ajax applications. Even if you have use the meta tags that specifies no cache, the IE7 would ignore them.
The above code does not work on IE7. You could force the browser to remove the cache by manually deleting it or by using the following code below in PHP:
// choose a date in the past
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
// set the last modified date to today
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
// if the browser supports HTTP/1.1
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
// if the browser supports HTTP/1.0
header("Pragma: no-cache");
Another way is to add the meta tag code below in between your end body tag and your end html tags. It does not conform to the w3c standards, but it works. :D