How do I set Apache set HTTP headers which cache all resources for 15 mins but also allow .htaccess files in a directory to override these settings on a per-site basis?
If you're talking about mod_expires (telling browsers how to cache the content), then you would put something like this in your httpd.conf:
ExpiresDefault A900 #15 minutes
And then in the .htaccess:
ExpiresDefault A3600 #1 hour
You can also override by type of resource, using
If you're talking about caching the content server-side (mod_cache), these directives can only be done in httpd.conf and vhosts files. .htaccess cannot override them.