1. sign in to imo
2
Click the context menu at the top right of the page to select a status. By default, your status will be set to “available”.
3
Select the “Invisible” option from the drop down menu to set your status. This will ensure all of your buddies will be unable to see when you sign in and out of the imo.im service. You will still be able to communicate with buddies.
RESOURCE : WIKIHOW