"What was essentially a typo last night resulted in the temporary disappearance from the Internet of almost a million Web sites in Sweden -- every address with a .se top-level down name.

According to Web monitoring company Pingdom, which happens to be based in Sweden, the disablement of an entire top-level domain "is exceptionally rare. ... Usually it's a single domain name that has been incorrectly configured or the DNS servers of a single Web host having problems. Problems that affect an entire top-level zone have very wide-ranging effects as can be seen by the .se incident. ... Imagine the same thing happening to the .com domain, which has over 80 million domain names."

The total blackout of .se lasted for about an hour and a half, Pingdom says, although aftershocks are expected to continue.

"The .SE registry used an incorrectly configured script to update the .se zone, which introduced an error to every single .se domain name," says Pingdom. "We have spoken to a number of industry insiders and what happened is that when updating the data, the script did not add a terminating '.' to the DNS records in the .se zone. That trailing dot is necessary in the settings for DNS to understand that '.se" is the top-level domain. It is a seemingly small detail, but without it, the whole DNS lookup chain broke down.""