You are probably trying to open facebook with the https protocol, which google may have glitched for some reason. Try opening facebook with the http protocol instead of https (the thing before http://www.facebook.com), and if that doesn't work, see if you can open it with a different browser. Clearing your cache never hurts and seems to be a solution quite often for no apparent reason, so I suggest you do that, too. If that doesn't work, try reinstalling google chrome. Hope it works.