> [JB] > >Expiry dates [to improve caching of static pages] > I'm not familiar with how they fit into the HTTP/HTML specification. > If you (or anyone) can provide the appropriate HTML meta tags with > a short explanation, I will add them to message pages. Index > pages may not be so easy as they are often rebuilt > (limitation of MHonArc) >
[LM] Using Expiry dates to help caching. Expiry dates for web pages can be set in two ways, the first is to use meta tags in the html, the second is to set the http header "Expires:" on the web server. Meta Tag <META HTTP-EQUIV="expires" CONTENT="Wed, 26 Feb 1997 08:21:57 GMT"> The tag needs to be set within the html <head> </head>. This tag should cause the page to be expired from the cache on "Wed, 26 Feb 1997 08:21:57 GMT". A script could be written to enter the tag in the html of the message pages and be set to expire months or years into the future. (There does not seem to be a way to say expire this page in so many days, rather than on this date). The problem with this is, that if the service is still going and you have taken the decision to never expire messages from your archive, eventually the message pages will need the expiry date updated. (A date that is in the past will be read as expire now.) Links pages could have the tag; <META HTTP-EQUIV="expires" CONTENT="0"> "0" (zero) in this case is an invalid date and is read as expires now, hence a page containing this tag would never be cached. See http://vancouver-webpages.com/META/ for more detailed information Web Server I know almost nothing about this, but it appears to be explained in the following links. http://vancouver-webpages.com/CacheNow/ http://vancouver-webpages.com/CacheNow/detail.html#expires **Note: In the above links they say that the level of caching in the US in low, but in Australia and likely all non-North American countries, every dial-up user goes through their ISP's cache (the equivalent of what the links call LAN caches). Suggestion >From my brief glance at the Web Server expiring and the problems I've outlined with the meta tags, it would seem that setting the http header expires through the web server would be the best way of dynamically assigning expiry dates. Regards Luke
