don't know about idle but if you get live plus you can personilse your status to anything you want from "in the shower" to "slowly strangling next doors cat"
I think idle is used when they haven't been using msn for a bit, but have been using the computer itself. Could be wrong on that though, but that's what I've always thought.
"Idle" is the status set by MSN when you have not used ANYTHING on your computer for a specified period of time.
In the options there is something to the effect of "Show as Away after XXmin".. If you leave your PC unattended (e.g. as if the Screensaver was to come on) then MSN will change its status to Idle.. as soon as you move the mouse or press a key it will default back to your set status, Online, Away, etc...