Some times I have issues with the wireless connection where I live. That issue is irrelevant to this (there are two IT departments managing this thing; there's nothing I can do about it). Most of the time it's nice and fast, but sometimes slows to a crawl (single digit KB/s sorts of crawl).
Anyway, I think Firefox (11.0 Ubuntu) might not be using its cache correctly. When (for testing purposes) I set it to "Work Offline", pages load on the order of a second. Normally, the same page (benchmarked on http://kb.mozillazine.org/About:config_entries ) loads in around three seconds when the connection is working properly, and ten or more when it's not. I can confirm it's reloading things, since I see a spike on my bandwidth-use graph while when I open the page. I think image caching is still working properly, since it doesn't seem to be very much bandwidth used though.
Shouldn't Firefox just be using the cached copy of the page (checked; exists in the disk cache) instead of downloading a new copy, when I open the page in a new tab?
I know that some content is set to expire, so it should download a new copy. I don't believe that the example page has one of those. Under "Work Offline", pages like gmail did not load, so I assume that that is the proper behavior of pages that expire.
How can I either make firefox use cache unless the page has expired, or, better yet, display the cached page while it tries to load a new copy?