Yahoo messenger allows people to stay in invisible mode. Do you want to find your freinds who may be in invisible mode. Invisible Scanner is a really good service that allows you to find out users who are online but in invisible mode. Invisible scanner allows you to scan 50 users in a span of 12 hours. The best part is you do not need to download any software. Check the site at http://www.invisible-scanner.com/
Good TryInvisible Scanner: Find yahoo users who are invisible371|just some value|7