For instance, when I revisit www.msn.com by typing the address into my address bar, IE issues 6 unconditional HTTP requests (to retrieve the resources which were marked as uncacheable on my prior visit). In contrast, if I use a META REFRESH to redirect to www.msn.com, like so:
<meta http-equiv=”refresh” content=”3;url=http://www.msn.com/” />
… IE issues 6 unconditional HTTP requests and 33 conditional HTTP requests to revalidate the page’s resources.
Interestingly, if your traffic is configured to go through a proxy, IE will also add a Pragma: no-cache header to the outbound requests generated from the META REFRESH. However, the If-Modified-Since and If-None-Match headers, if any, are not removed, so unless the proxy or server respects the Pragma directive, 304s may still be returned.
<meta http-equiv=”refresh” content=”3;url=http://example.com/ThisSiteRequiresScript.htm” />
Since browsing with script disabled is fairly uncommon, that scenario probably isn’t much of a problem for real-world sites.
Until next time,