This is happening a lot lately. Just now it didn't happen, but you know how it looks (see here for a screenshot).
I was worried that this could be a duplicate, but:
I've tried clearing the cache, and switching browsers, and apparently the only thing that works is connecting to Stack Overflow through Tor (gives me a different IP address - BTW this might prove item d is not the case). Are you using any kind of IP address-based caching?
Surprisingly, at this hour it renders fine and quickly. Might be some kind of traffic overload?
I'm on Ubuntu 13.04 (Raring Ringtail) using Firefox 22.0.