I am trying to figure out what the `errors` endpoint is used for, so I can I can implement it in my API.  

I have been trying things like:

 - http://api.stackoverflow.com/0.8/errors/404
 - http://api.stackoverflow.com/0.8/errors/0
 - http://api.stackoverflow.com/0.8/errors/1
 - http://api.stackoverflow.com/0.8/errors/500

All the errors help page says is:

>**Summary**  
Simulates an error given a code 


What are valid error codes?  And, can we get some sort of response telling us that we supplied a bad error code?