I guess it could be, but personally, I think that there seems to be a slight difference.
You could be offline without being logged out. For example, someone could appear offline in a chat just because they closed the tab, not necessary logging out of the chat (as in the next time they opened the chat tab, they wouldn't have to write username and password all over again, they would already be logged in, and online.)
That might be just me though. xD
Ah, yes, that's actually a really good disambiguation. Many thanks Dimitra!
Jaye, it's becoming apparent that we are learning to use our computers in Greek-language programs (now called applications). Can you suggest where one might start, so that one can actually get some experience with such computer messages?