iWork.com is dead. Long live iWork.com!
Today is the last day that you'll be able to sign into the iWork.com beta. Apple's first attempt at creating a document sharing environment for Pages, Numbers, and Keynote documents never did make it to prime time. Tomorrow, iWork.com goes the way of the dodo and MobileMe.
Any documents you have stored on iWork.com should have been moved to your iCloud account, provided that you used the same Apple ID to sign into both iWork.com and iCloud.
If your documents somehow failed to make the transition to iCloud or if you just want to move them back to your Mac, Apple has full instructions here on how to download those precious files.