Отсюда:
# ----------------------------------------------------------------------
# Expires headers (for better cache control)
# ----------------------------------------------------------------------
# These are pretty far-future expires headers.
# They assume you control versioning with filename-based cache busting
# Additionally, consider that outdated proxies may miscache
# www.stevesouders.com/blog/2008/08/23/revving-filenames-dont-use-querystring/
# If you don't use filenames to version, lower the CSS and JS to something like
# "access plus 1 week".
<IfModule mod_expires.c>
ExpiresActive on
# Your document html
ExpiresByType text/html "access plus 0 seconds"
# Media: images, video, audio
ExpiresByType audio/ogg "access plus 1 month"
ExpiresByType image/gif "access plus 1 month"
ExpiresByType image/jpeg "access plus 1 month"
ExpiresByType image/png "access plus 1 month"
ExpiresByType video/mp4 "access plus 1 month"
ExpiresByType video/ogg "access plus 1 month"
ExpiresByType video/webm "access plus 1 month"
# CSS and JavaScript
ExpiresByType application/javascript "access plus 1 year"
ExpiresByType text/css "access plus 1 year"
</IfModule>
