If I log into someones yahoo email and messenger from my computer can they tell on their computer?

yes it will log them out if they are on and it will say "you have been logged out because you logged in at another location"





They won't be able to tell if they are not online.

If I log into someones yahoo email and messenger from my computer can they tell on their computer?
You can check their email without them knowing but if you log into yahoo messanger they will immediately be logged out and get the message "you have been logged out because you logged in at another location": but it will not disclose where or who logged in. If you do check thier mail be sure to click 'mark as unread' or they will know someone has been there.
Reply:They know you were THERE...............
Reply:If you log onto their messenger and they are in messenger as themselves they will know because it will boot them out. then if you are logged in as them and it boots you out you know they logged back in. also for email if you log in as them they would know if you logged in because they would see unread messages they have not seen yet as read.
Reply:yes...they get booted


and a message comes up that they are sharing their files with another person.