The PSN is going down for quite a long period of time today. In fact, if you try to sign on right now, you probably won’t be able to. It’s being taken offline from 8:30 A.M. Pacific time to 2:00 P.M., which means it’s going to last until 5:00 P.M. on the east coast. As if daylight savings time wasn’t screwing with your head enough.
If you have signed into the network since March 6 th , you will be able to play online games and access partner apps such as Netflix while the network is down. However, the PlayStation Store, PlayStation Home, and PlayStation Account Management will all be inaccessible.
Source: PlayStation Forums