Facebok Goes Down: 'Internal Prototypes' To Blame

Had trouble getting on Facebook earlier today? You weren't alone.
Facebook was down for many users at around 4:00PM ET on Thursday.
Facebook explained the outage after the site was back up and running:

For a brief period of time, some internal prototypes were accidentally exposed to people externally. As a result, we disabled the site for a few minutes. It's back up, and we apologize for the inconvenience.

Mashable confirms that the outage took place around 4:15 p.m. (ET), around the same time the site began rolling out redesigned brand Pages, a new Photos section and a new Page management feature.