Date: 15-07-05 03:16
I've started to add Last-Modfied and ETag to the headers on the website. For example, you should see something like this on the headers for each page in the website:
[dan@polo:~] $ wget -S http://www.freshports.org/authors.php
Resolving www.freshports.org... 188.8.131.52
Connecting to www.freshports.org|184.108.40.206|:80... connected.
HTTP request sent, awaiting response...
HTTP/1.1 200 OK
Date: Fri, 15 Jul 2005 03:14:49 GMT
Last-Modified: Fri, 15 Jul 2005 03:10:45 GMT
ETag: "2005-07-15 03:10:45"
Length: unspecified [text/html]
[ <=> ] 13,263 58.44K/s
23:15:45 (58.34 KB/s) - `authors.php' saved 
There are a few more pages to complete. I documented the list in http://dan.langille.org/2005/07/10/are-your-php-pages-observing-last-modified/.
If you see any problems, please let me know.