Notifications is one of the features that is available now in CRM 2013. We used to implement it in an unsupported manner in CRM 2011.
This is how we can set the notification using the setFormNotification method
Xrm.Page.ui.setFormNotification(message, level, uniqueId);
Message – the message to be displayed.
Level – ERROR, INFO, WARNING (will show the corresponding icon).
UniqueId – to identify the notification to be used for clearing it.
The way we used to implement it in CRM 2011.
In CRM 2013, we can also set notification on a particular control.
The form will not be saved unit the notification is cleared from the control.
Message while trying to save the form without clearing the notification:-