Obviously no-one has been flying or else the backup has worked so smoothly that no-one has felt the need to comment.
The site apparently went down late yesterday afternoon and is still down at the moment. There is a redirect link on the screen to the NATS contingency site where briefings are available.
The suppliers (Thales IS) are working on the problem which only affects the Web Server. The main database and any commercial briefing services that link in to it are unaffected.
When it comes back up you might find that the redirect page is cached by your browser and you will need to refresh your screen to get the login page back. (Ctrl + F5 in Internet Explorer)