Fairly often, when I click on the "earlier" link on my LJ friends or friendsfirends page, it shows me a stale page. I've gotten good at noticing that and hitting reload, but it's annoying. This only happens about one time in five -- most of the time, clicking the link does cause it to reload. Why is it behaving so randomly?

I think maybe I could make this go away by selecting "every time" instead of "when the page is out of date" in Mozilla's cache prefs, but I think that will also make Mozilla go to the network when I hit the Back button, which would suck. I want it to send an If-Modified-Since every time I actually click a link, but use the cached copy for the back button. I think that's how it always used to work. Has something changed?

Is it Mozilla being stupid, or LJ?