I observe this few weeks ago,, there is a lot of account user in yahoo who is appear online even if the real user of this account is not logging in.
We call it spam and the messages are:
*"I just took an IQ quiz here.. pretty cool"
*Haha I just scored 82 on this IQ test.
If you are a yahoo users and experiencing this kind of spam, the solution is very simple.
Go to your yahoo menu then right click the user name of the spammer, you can see the delete option showing in the last portion. Click delete and also mark the delete in address book too.
Go to the yahoo window of the user name that you already deleted.
Click the ignore button and also report as spam.
Just take a look at the pix for easy instruction.