Sometimes when i'm on forums, this screen appears. I know that i have to click the red button on top-right. I just want to know what happens. Because the server goes offline, but when i refresh it, it is immediately online again. So, this little crash lasts a very short period of time.
I have never seen this kind of problem in other sites, so i'm just wondering what happens.

Is just a problem that the forum sometimes has. It isn't from your PC or browser is from the forum. Just wait some minutes it will dissapear, i had it too for to many times.

You're supposed to click the green button: "Retry for a live version"

It fixes the problem for me instantly.

As i said, i know how to fix it. Just wondering why sometimes the server goes does down for some seconds, is it a refresh or something to clear database?