This page sends a "Last-Modified: Yesterday/Now" HTTP response header
Last-Modified: Tue, 22 May 2012 06:42:04 GMT
and should respond with 304-Not Modified if you request it (twice) with an "If-Modified-Since: Today/Now" HTTP request header:
If-Modified-Since: Wed, 23 May 2012 06:42:04 GMT
(Please read the tutorial, and here is a tool to test Last-Modified/If-Modified-Since/Not-Modified functionality.)
Here is your HTTP request header:
[GET:] /tools/last-modified-yesterday.php
[Accept:] text/html,application/xhtml+xml,text/xml;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
[Accept-Charset:] ISO-8859-1,utf-8;q=0.7,*;q=0.7
[Accept-Encoding:] gzip
[Accept-Language:] en-us,en;q=0.5
[Cache-Control:] no-cache
[Connection:] close
[Cookie:] tools=www.sebastians-pamphlets.com%2Fthou-must-not-steal-the-trailing-slash-from-my-urls%2F
[Host:] sebastians-pamphlets.com
[Pragma:] no-cache
[User-Agent:] CCBot/1.0 (+http://www.commoncrawl.org/bot.html)
[x-cc-id:] ccc01-02
If-modified-since: Thu, 01 Jan 1970 00:00:00 GMT
Last-modified....: Tue, 22 May 2012 06:42:04 GMT