I'm trying to do something which I thought would be fairly simple: get IIS 7 to tell clients they can cache all images on my site for a certain amount of time, for example 24 hours.

I have tried the step on http://www.galcho.com/Blog/post/2008/02/27/IIS7-How-to-set-cache-control-for-static-content.aspx to no avail. I still get requests going to the server with 304s being returned.

Does anyone have a way of doing this? I have a graphically intensive site and my users are being hammered (so is my server) every time they request a page. Weirdly the images seem to have "Cache-Control private,max-age=3600" showing up in Firebug, but the browser is still requesting them when I press F5.