That may be just a holding page for the company that hosts the web site. Personally, when redesigning web sites I get everything tested on my local PC, then clear down the host files and upload the complete set of new files. Takes about ten minutes, and best done in the wee small hours when your visitor traffic is lowest. Even when changing host company it is best to put the new files on both the old and new IP hosts so when Nominet switches it over it will look seemless. In any case do not shut the old site content until the new is ready to roll.
I can't understand why a popular web site goes offline 'for updates' or just sits there with an 'under contruction' label.