A notification banner, first noticed by MacRumors, which bares a striking resemblance to iOS notifications introduced with iOS 5, appears to only be a placeholder. It is vaguely titled "Default Title for English" with a message of "English - This is a test message description."
The message appears when you log in to your icloud.com account directly from the Web site.
Apple's preview of Mac OS X Mountain Lion shows off a similar banner notification system, which may be related to the iCloud notifications. Certainly syncing notifications across all iOS devices and your Macs could help ease the burden of checking and acting on every notification on every device you own.
Notifications on iOS alert users about everything from new Mail messages to text messages to new levels on Angry Birds. Options can be customized for your apps by navigating to Settings > Notifications and tapping on each app.
Apple introduced iCloud to replace MobileMe as the de-facto sync tool for iOS devices and PCs and Macs. iCloud users are able to sync their calendars, contacts, mail accounts, and notes, as well as locate their iOS devices and Macs using the Find my iPhone/iPad/Mac apps.
Would you want synced notifications across all your devices? Let me know your thoughts in the comments!