In .2a, Vary: is now sent by default, but it has a very
harsh interaction with requests. It seems that
*EVERYTHING* is being sent with a Vary: header, rather
than those things which match the includes/excludes
specified in httpd.conf.
Besides the fact that this will cause later Squid to
take up much more room for caching for an entire site,
this is causing some bizarre problems. (Among them,
MSIE5 apparently gets very confused about image/*
carrying a Vary: header, and ends up not capable of
right-click-and-save on images if this happens. Rather
than saving the image file, a BMP is saved...!)
Basically, it looks as if mod_gzip should be reversing
the checks for include/exclude and Accept-Encoding so
that Vary: can be sent properly (on *only* those URIs
which would elicit varying behavior thanks to mod_gzip).