How does that work? Do they say how they test?
I'm assuming they've got a bunch of servers all around the world that ping the website?
What happens if you can't access it? How do I find out if downforeveryoneorjustme.com is down for everyone or just me?
If you can't get on to downforeveryoneorjustme.com, my advice is to send an email to everyone in the world and ask them. Its the only way to be sure