I just recently moved to a VPS. I reinstalled WP and of course W3TC. I turned pretty well everything on, including all browser caching. Under the Browser Cache heading in W3TC, I've checked everything off, except for "Prevent caching of objects after settings change". I've left the 404 exception list as the default, as well as all lifetimes and have selected "cache with max-age" for cache control policy, wherever possible.
However, when I test the site on webpagetest.org, I still get this:
FAILED - (No max-age or expires) - http://example.com/wp-content/themes/vigilance/images/sidebar/rotate.php
FAILED - (No max-age or expires) - http://example.com/index.php?ak_action=aktt_js&v=2.4
FAILED - (No max-age or expires) - http://example.com/index.php?ak_action=aktt_css&v=2.4
FAILED - (23.1 minutes) - http://example.com/
WARNING - (12.0 hours) - http://www.google-analytics.com/ga.js
I wasn't quite sure if there was a way to fix or remedy this. Or whether it's really anything to worry about. Still quite happy with the speed of the site.