"Routine scheduled maintenance" is about to hit the PlayStation Network, making it unavailable for users for about thirteen hours today. From approximately 8AM to 9PM PST (11AM to 12AM EST), the following PSN services will be unavailable: PlayStation Store, PlayStation Network Account Management & Registration, and PlayStation Home. In addition, Music Unlimited and Video Unlimited services will be unavailable. You will also be unable to sign in to the PlayStation Network on the web, either.
The system-wide maintenance period will mean that gamers will be unable to play online... unless they're already signed into the PSN before the maintenance period begins. "Users who are already signed into their account on PlayStation Network before the start of the maintenance should be able to stay signed in to their online session," the PlayStation.Blog notes. "But will not be able to access any of the services listed above. Users who attempt to sign-in to their PlayStation Network account after the start of the maintenance may be presented with the site maintenance notification page if they haven’t signed in recently."
As always, you can continue to earn Trophies during the PSN downtime, and sync then once the service is up again.