User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8 ( .NET CLR 3.5.30729; .NET4.0E) Build Identifier: 3.6.8 Firefox will not correctly interpret a server response containing a valid “Expires” and “Cache-Control” header which equate to a future date/time which is intended to instruct Firefox to cache the response. The page’s head must also contain either or both: <meta http-equiv='X-UA-Compatible' content='IE=edge' /> <meta http-equiv='imagetoolbar' content='no' /> The cached object can be found in Firefox’s “about:cache” (disk cache). However, Firefox will ignore the cache approximately 50% of the time and instead request the page again. This bug has been demonstrated in Firefox 3.6.8 and Firefox 3.0.4. Presumably other versions are affected too. Either or both the aforementioned meta tags must be in the page’s head but may not be limited to just these two meta tags. Other factors that have not yet been determined may be involved in reproducing this bug. Reproducible: Always Steps to Reproduce: 1. Add valid “Expires” and “Cache-Control” header which equate to a future date/time. 2. Add <meta http-equiv='X-UA-Compatible' content='IE=edge' /> Actual Results: Firefox request a new page approximately 50% of the time. Expected Results: Firefox should be displaying a cached page It goes without saying that this bug causes Firefox to produce undesirable network traffic and additional load on servers and therefore this is problem that should be addressed. The meta tag “<meta http-equiv='X-UA-Compatible' content='IE=edge' />” involved in influencing the problem is likely to exists on many websites including popular ones and therefore this problem may affect a great many sites. Thank you for your consideration.

The image shows Firefox 3.6.8 making requests for a page that should have been displayed from Firefox's cache.

Fixed in Firefox 4 betas.

And I'd like to thank you for a clear and understandable bug report! It's very much appreciated.

(In reply to comment #2) > Fixed in Firefox 4 betas. > > *** This bug has been marked as a duplicate of bug 567360 *** Hi, I am glad to read that this problem has been corrected for future Firefox versions. However, as a web developer I must be concerned about the millions of other persons using FF <4 which have this bug and therefore must have a workaround to the problem. With that said, where can I find detailed information about the problem and which meta tags cause the problem if not only those that I’ve discovered.