On several sites (Some mozilla, some not) css doesn't show up, even with many reloads, and clearing cache.

I've been seeing this for a few weeks now, especially on Bugzilla, clippercard.com, my bank website, and other places. I can usually temporarily get it to fix itself by doing shift-reload, but it comes right back the next time I load the page. This has made me open Chromium more than once just so I can view a website correctly. :/

I was seeing something like this frequently, but haven't seen it in the past few days: http://grab.by/6n6v I thought it might be related to bug 513008 (possibly fixed the fixing of bug 589296?).

I'm seeing it on bmo right now. The top yellow bar is missing until I do shift-reload.

Reed, what was the time (and build) you have seen this the first time? And what build version are you using saying you see it "right now"? Loading this bug's page and some bugzilla results with mozilla-central debug build old just an hour are OK.

Blocking, but my money is on this being a dupe of bug 588804.