phranque - 2:34 am on Feb 5, 2011 (gmt 0)
it depends on what determines a "significant" change in content for your specific application.
if you are basing it on all 3 options (inode, last modified and file size) it would be simpler to use:
if you are using a CDN, for example, the inode would be different on each server, so you might want to use:
you also want to make sure this directive is designated in the proper Context [httpd.apache.org].