The PlayStation Network will be undergoing downtime today as part of a scheduled maintenance window. The PSN will go offline at 5:00PM BST (10:00AM MDT / 11:00AM CDT / 12:00 noon EDT) and will last for approximately 7 hours, until 12:00AM midnight (5:00PM MDT / 6:00PM CDT / 7:00PM EDT).
The maintenance period will only affect North America. Games in Europe should experience no issues.
Specifically during the first hour of this maintenance period, you may receive a maintenance notification when attempting to access PSN. The PlayStation Store and Account Management will not be available during the maintenance period but you will be able to access online play and apps provided that you have signed in to the Network before the maintenance window.