When I reopened Firefox after a few hours, it normally opens the last website I've viewed, but it displayed for a second a strange message popup similar to:
There is a more recent version of the page on the server, do you want to reload?
(maybe it's not the exact phrase because of my translation and that I may have not read the popup correctly).
I opened Firefox about 4 hours before, then left Firefox on standby on the phone. Then I reopened the site without refreshing when I saw the notification above.
I have no malware on the smartphone, and it was just a normal website about cars.
What does the notification mean?