1. A method comprising: detecting, using one or more processors, an alert in accordance with an alert registration, wherein the alert registration: is associated with a particular subscriber of an online communication system that allows subscribers to communicate, share information, and interact with other subscribers, and is associated with a particular client application; determining that a client system associated with the particular subscriber is online but not running the particular client application; and enabling presentation of a notification of the alert to the subscriber when the client system is online but not running the particular client application.