Just like every year Apple gives their App approvers a week off around Christmas, this means that iTunes Connect will be offline, during this time you cannot submit an application for approval to the App Store, furthermore you will not be able to submit app updates, price changes, or in-app purchases, this also means that Newsstand publications will not be updated, even if a new issue is available.
According to a message on iTunes Connect
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.