Someone caused an update to be made on Facebook’s Boarder Gateway Protocol (BGP) records.
Boarder Gateway Protocol – Is the post service of the internet.
For example, when you post a letter into the post box, the post office then processes that letter and chooses a fast, efficient route to deliver the letter to its recipient.
Similarly, when you submit data across the internet. BGP is responsible for looking at all the available paths that the data could travel and selecting a fast, efficient route.
In simple terms someone at Facebook took away the map telling the worlds computers how to find its various online properties. So, when you typed Facebook.com yesterday into your browser, the browser had no idea where to find Facebook.com and returned an error page.