Is it you or is it me?

Here's a handy site that lets you figure out whose fault it is that you aren't able to get onto a given Web site - Is it the site's fault? Or your own?

I found out about it from this New York Times story. I wish I'd known about it last week when I was trying to determine why I was being diverted away from the Pasadena Star-News site to a warning page, although it wouldn't have answered all of my questions.