I've got a site having a rotatory banner, and there's a JavaScript that implements the rotation. I've instructed Apache to come back Expires header for those images for some time later on (maybe 12 several hours) something it's doing each time. The issue is Opera (and also the others I suppose) is asking Apache for that validity from the image each time the banner image is transformed. I believe the best behavior is perfect for would be to request Apache once the images aren't longer fresh (following the 12 several hours have passed) however there's always a round-visit to request and also the server to reply a 304 Not Modified. I have to eliminate these round-trip to relieve the already loaded web server.