I have a site with a rotatory banner, and there is a JavaScript that implements the rotation. I have instructed Apache to return Expires header for all images for a time in the future (maybe 12 hrs) something it is doing every time. The problem is Firefox (and the others I assume) is asking Apache for the validity of the image every time the banner image is changed. I think the right behaviour is for is to ask Apache when the images are not longer fresh (after the 12 hrs have elapsed) however there is always a round-trip to ask and the server to respond a 304 Not Modified. I need to get rid of these round-trip to alleviate the already loaded web server.