Turn Your vBulletin On and Off 
This setting group from the vBulletin options will allow the Administrator to close the forums to the public with a custom message or set it active. This is a usefull feature when performing serious forum or database maintenance, version updates or bug fixing.

Only users in the Administrator usergroup will be able to browse the site, visitors will be presented with a closed message which you can set in this setting group.
User Contributed Notes: Turn Your vBulletin On and Off Add a Comment