Ever tried to load a site in your browser just to end up with nothing yet still thinking “is this a local problem” or IS the site REALLY down?
Well I just stumbled over a site that will assist you in your debugging;
http://www.downforeveryoneorjustme.com/
Here you enter the site you wish checked, and the server checks if the site is loadable from its end. Yes I know this is a very basic check, however it may come in handy some day.