Most proxies, most notably Squid up through version 3.0, do not cache resources with a "?" in their URL even if a Cache-control: public header is present in the response. To enable proxy caching for these resources, remove query strings from references to static resources, and instead encode the parameters into the file names themselves.
labs / experience
Web Site Optimization - Remove query strings from static resources
legacy
updated: 2013-01-10
reading: 1 min
Legacy note: archived and kept for reference.