Instructions
Turn on your PS3 console and scroll to the "Settings" icon on the far, right side of the XMB menu.
Scroll down to the "System Settings" option and press the "X" button on your PS3 controller to select.
Select the "Notification Messages" option and click on "Do Not Display." Press the "Circle" button on your PS3 controller twice to save the settings and go back to the XMB menu.