When a network problem strikes, it isn’t always immediately obvious. It’s rare to get a clear message on the screen, and it’s easy to imagine that Facebook has simply crashed or a website is temporarily offline. A good first check is to open a new window in Safari and try pointing at google.com. The web requires the least complicated protocols of any of the services that run over the internet, and Google has a nice fast webpage that is always up. The front page itself could be loading from Safari’s internal cache, of course, so test your live connection to the internet by typing something random into the search box to force it to query the server.