You'll be unable to access the store or play online until around 7:00 PDT, 10:00 EDT.
The folks at Sony have shut down the PlayStation network for some routine maintenance today, which will prevent gamers from accessing Home, Account Management, the PlayStation Store and from playing games online.
Maintenance will end at 7:00pm PDT / 10:00pm EDT, so those living on the east coast will need to find something else to do tonight. Time to dust off one of those "man, I always meant to finish this" games.
PlayStation says to keep an eye on their Twitter feed for the most up to date info on the downtime.
Source: PlayStation Blog