OK. Here is a mock example of an IM with my brother...

me: (1:00:00pm)Hey.
bro: (1:00:30pm)Hey.
bro: (1:00:45pm)How are you?
bro: (1:00:47pm) Hello?
bro: (1:00:49pm) Hello hello? Are you still there?
bro: (1:00:53pm) HELLO HELLO HELLO!!!!
me: (1:01:30pm) I'm fine.

If you are ever IM-ing with my brother, apparently you have to answer his AS SOON AS TEMPORALLY POSSIBLE, or else he thinks you've been killed by a boulder, eaten by a shark, taken hostage by some splinter group, or abducted by aliens.

Just remember that.