How do you tell if a problem is caused by DNS?

I was looking into problems people were having with DNS a few months ago and I noticed one common theme – a lot of people have server issues (“my server is down! or it’s slow!“), but they can’t tell if the problem is caused by DNS or not. So here are a few tools I use to tell if a problem I’m having is caused by DNS, as well as a few DNS debuggging stories from my life. I don’t try to interpret browser error messages First, let’s talk briefly about browser error messages. You might think that yo...