(This is forwarded from Yngve N. Pettersen at his request. I don't know whether this server issue should be our problem, personally.)

https://popehat.com, incorrectly, perhaps based on some issue in its scripting or file update system, sends this response header:

  Last-Modified: Thu, 01 Jan 1970 00:00:00 GMT

Which of course results in the chromium network code sending

  If-Modified-Since: Thu, 01 Jan 1970 00:00:00 GMT

Since the server believes that everything was modified at the epoch, it mightn't send an updated document.

I would suggest that at least any date as old as that should be ignored, and the header should be ignored. It's been a long time, so I am no longer confident I remember correctly, but I seem to recall that I added such code in the old Opera code.

Another item is that I am actually seeing this header being sent for full reload (F5) requests, too, when the "Cache-Control:max-age=0" header is sent. Sending If Modified since in a reload request is IMO not just unnecessary, but I wouldn't be surprised if there are misconfigured/buggy servers that might prefer the that header to the the cache control header. Perhaps it might be better to avoid such potential for confusion?