Regarding this resource (the file is also attached to this post): http://xenforo.com/community/resources/avatar-php.634/ I can't get browser caching to work. The avatar images are re-downloaded by the browser on every request. It appears to be the same problem described here: http://stackoverflow.com/questions/...rn-304-not-modified-if-it-hasnt-been-modified I have experimented with various headers including: Cache-Control Expires ETag If-None-Match I can manually return the 304 status code in the script, but on what condition? I have been unsuccessful in getting any kind of cache validation to work. And I can't arbitrarily return 304 on every request or it won't download on the initial request. I welcome any ideas.