As is customary for Apple during the holiday period, iTunes Connect is set for some downtime. This year, the developer service will be offline from December 21st until December 27th. For those of you unaware, this means that devs will not be able to submit new apps, updates or price changes during that time.
Apple sent the following email to developers (via iMore):
iTunes Connect will be temporarily unavailable from Saturday, December 21, to Friday, December 27, 2013.
During that time, iTunes Connect will not be accessible and you will not be able to submit any apps or In-App Purchases. Processing of any Newsstand Atom feeds will be delayed until after December 27. Sales and Trends reports via the Autoingestion tool will be available but may also be delayed.
Also, you should not schedule any pricing changes or apps to go live between those dates. Pricing changes scheduled to take effect in that date range will cause the app to become unavailable for purchase until after December 27. Similarly, apps scheduled to go live during that range will not be released until after December 27.
If you have any additional questions, use the Contact Us module on iTunes Connect.