How to use browser caching with Amazon S3?

Question

I get the following on gtmetrix.com:

Leverage browser caching    
E (55)
52%
Server  High
What does this mean?
The following cacheable resources have a short freshness lifetime. Specify an expiration at least one week in the future for the following resources:

http://mysite.s3.amazonaws.com/profile.png (expiration not specified)
http://mysite.s3.amazonaws.com/circle.player.css (expiration not specified)
http://mysite.s3.amazonaws.com/main.js (expiration not specified)
http://mysite.s3.amazonaws.com/not.the.skin.css (expiration not specified)
http://cdn-images.mailchimp.com/embedcode/slim-321711.css (expiration not specified)

I'm guessing the mailchimp files can't be modified. But how do I specify a browser cache for Amazon S3 Cloudfront files?

Answer 1

Via Amazon Management Console, select your file (or folder).

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Go to the Properties tab and click on Metadata.

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Finally, add Cache-Control to its header and save.