2. Use the directives provided by mod_expires to set an explicit expiration time on your files, thereby letting browsers and proxies know that it is acceptable to cache them.
I added this to the .htaccess file of a specific folder so that I could get a way around shtml files not showing last modified dates:
ExpiresByType text/html "modification plus 60 days
The additional headers I got were :
Expires Fri, 06 Feb 2009 17:05:56 GMT
And the lastmod date and times keep being the current ones with "Use server's response" setting.
Shouldn't XML Sitemaps use the original date and not refresh the date to the current date and time every time it re-crawls?