refer to http://stackoverflow.com/questions/896974/apache-is-not-sending-304-response-if-mod-deflate-and-addoutputfilterbytype-is
http://scarff.id.au/blog/2009/apache-304-and-mod_deflate-revisited/
Fix solution:
#add following to .htaccess or httpd.conf<IfModule mod_headers.c>RequestHeader edit "If-None-Match" "^\"(.*)-gzip\"$" "\"$1\""
</IfModule>
原文：http://www.cnblogs.com/jmbkeyes/p/4108390.html