er... If you are wondering whether an admin can tell who has been on an account and when...then the answer is obviously...yes. If you are worried about it, then spoof your IP before you login. I don't see why the admin would bother checking unless he has a complaint from the person who owns the account. If you are talking about logging into an admin account, then the admin will probably find out someone was on it, but as long as you fix the logs, cover your footprints, and don't do anything stupid (ie. dont send out e-mails all across the world to your buddies to show them you are cool cos you rooted a box) you should be fine.
"I have been driven to my knees many times, because there was no place else to go."