audreyr/favicon-cheat-sheet — pull request #15 by noahcollins (2013-09-04 00:06:16+00:00)
Title: Cache busting: query strings not 100% effective

There are rare edge cases where query strings are stripped by proxies and load balancers. To be comprehensive, it's good to mention the safest method: putting the version number in the actual filename

Here's some good discussion with examples. http://stackoverflow.com/questions/9692665/cache-busting-via-params