Forum OpenACS Q&A: Response to MS Proxy Server and Caching Problem with OpenACS 4.2 Web Site

Cache-Control: private indicates that the resource is cacheable but potentially different for every recipient, so shared caches (squid, MS Proxy, etc) should not cache it while private caches (your personal browser cache) can consider it fully cacheable. While this is how we want ACS pages to be treated it's probably not what you want for static HTML. No biggie, really, but it means some content you're serving isn't being treated as cacheable when it potentially should be.