Visitors to Facebook, on Thursday night, were presented with a blank page as the site disappeared momentarily for around 15 minutes.
A quick look at the time of the page source suggested that the code had disappeared completely, with the home page offering nothing more than html commands.
Experts believe that it might have been something to do with a number of changes Facebook made on the day in question.
UPDATE: The site is now accessible.
UPDATE 2: Facebook has acknowledged the downtime via its Twitter account:
"Facebook is available again after being down for a brief period. We apologize for the inconvenience".
However, it has as yet declined to say what happened.
UPDATE 3: A bit more information has been dished out, again via Twitter:
"Also, some internal prototypes were exposed to people and resulted in us disabling the site briefly. It's now back to normal".