isthewebsitedown if you are asking, probably not. if I am asking, probably so

Most useful new content to come from Yahoo(!) in years.

This is a very good overview of the public DNS system. Kinda gives you a feel for the fragile nature of the beast. Also, it gives some great information on the role that crap DNS plays in hidden performance problems.

Of course, I love using OpenDNS for testing, as most ISP's DNS servers just plain suck.