The "If-Modified-Since" header is something the browser sends to the server, to indicate it's got a copy from such-and-such a date. That gives the server the opportunity to tell the browser that the old copy is still current.
This would not be a header you would add to your script...or any page being send *from* to server.
It is primarily intended for static files. While there could be some useful applications for considering the browser's If-Modified-Since request in a dynamic script, I doubt it would be fruitful for most typical dynamic pages.
FWIW,
-dave
ps. To get a comprehensive understading of the HTTP protocol, I can't recommend enough the book "Web Client Programming with Perl" by Clinton Wong [O'reilly, 1997...$5 used on Amazon] (even if you don't know perl) and the application HTTP Tracer ($25 from
http://www.lazydogutilities.com/) . You'd be *amazed* how HTTP Tracer can help you cut to the quick of a problem when nothing else is making any sense.
--
David Hempy
Internet Database Administrator
Kentucky Educational Television
(859)258-7164 - (800)333-9764
Sent by Joe Goldsmith on 04/06/2004 08:55:19 PM:
Make sure your web server supports the If-Modified-Since HTTP header. This feature allows your web server to tell Google whether your content has changed since we last crawled your site. Supporting this feature saves you bandwidth and overhead.
How would I add this to each page using FoxWeb?
Joe