Understanding and using Groups in Yahoo! Messenger
This article explains how to organize your Messenger contacts into groups.
Groups help you to organize your contacts into categories.
For example, you could use groups to organize Chat Friends, School Friends, Co-Workers, and Family.
To move a friend from one group to another, please click the contact's name and drag it into another group.
When the arrow next to a group points to the right, you're hiding the names in that group. You can click the arrow to switch between hiding and showing names.
Note: Please understand that while there is no limitation to the number of contacts within a single group, the Messenger contact list can only contain a maximum of 1000 contacts. You can create up to 30 groups.