How does a server distinguish between a page request coming from the link "Show unread posts since last visit." (the one on the top of each page, near the user's avatar) versus the same address, "
https://www.eevblog.com/forum/unread/", coming from a refresh (F5) action?
I am asking this because:
- before the database maintenance, I had 502 Err here and there, maybe once in a week, and the err goes away by itself at the next access of the same link
- after the database maintenance, the two links near the avatar were ALWAYS returned 502 err for me. I testes it many times, I tried them maybe 20-30 times over a couple of hours. Always 502 Err.
- then, after one F5 for each link, the 502 Err has gone forever. I didn't saw a 502 Err since then.
Of course, this might be just a coincidence, but it's very hard to believe.
The most probable explanation to me is that the server has received a different type of request for the F5, compared with the request coming from the link "
https://www.eevblog.com/forum/unread/". That different request, apart from re-sending the page, also permanently fixed the 502 Err.
Seems to me that F5 is sending something else then just the URL from the address bar, or at least is doing something different on the browser side.
So, my curiosity is: What exactly does a browser send/do when I press F5, compared to a simple click on a link, please?