“CAUTION: provisional headers are shown” in Chrome debugger

Question

I noticed a strange caution message when looking at downloaded resources using Google chrome inspector (F12):

Caution provisional headers a

Answer 1

Another possible scenario I've seen - the exact same request is being sent again just after few milliseconds (most likely due to a bug in the client side).
In that case you'll also see that the status of the first request is "canceled" and that the latency is only several milliseconds.