Site vs File (Browser Caching) Different? Why?

[robzilla]

Quote:But if you try the images directly (@either cdn. OR forum.) they will pass with flying colors

They don't, actually. Compare these results:
http://www.webpagetest.org/result/131007...1/details/
http://www.webpagetest.org/result/131007...1/details/

Both show that navigation-tab.png has no expiry headers. Some other images do, however.

My guess is that you set up caching headers for these images after CloudFront first fetched them from your server. Not just the images, but also the headers are cached by the CDN at the initial pull request. To update the header contents, you'll need to purge these resources from CloudFront's edge servers. You can do this fairly easily from the AWS panel.

If you're pushing your resources manually to CloudFront, rather than having them pulled from your server at the first request, you'll have to manually correct the headers (in S3 or wherever you store them).