If you get this error message it means you are using API V2.
In Version 2 Google ask to register to be able to use Google map embedded into your website (except localhost).
In version 3 you do not need a key anymore as long as you are no using it “intensive”. See Google maps docs.
The link used in your error message is wrong (was not updated by Google).
To get a valid key visit:
http://code.google.com/apis/maps/signup.html
Advice: Have you time, then just jump to Version 3. It is really really GOOD!



