Option Name:refresh_all_ims
Default Value:refresh_all_ims off
Suggested Config:

	When you enable this option, squid will always check
	the origin server for an update when a client sends an
	If-Modified-Since request.  Many browsers use IMS
	requests when the user requests a reload, and this
	ensures those clients receive the latest version.

	By default (off), squid may return a Not Modified response
	based on the age of the cached version.