All error messages are returned as XML.
<error errorCode="400" errorString="Empty Query" />
2XX Database Errors Database errors indicate there was an internal problem with the API system. 3XX Account Limitation Errors 300 Account monthly Query Limit has been exceeded 301 User Supplied Queries Limit exceeded 302 Account is suspended 303 Account is suspended 304 Account is pending, awaiting processing 305 Access to the Query function is disabled 306 Access to the Multiple Query Function is disabled 307 Access to the Spell Function is disabled 4XX User Input Errors 400 Query String is Invalid 401 Offset value is Invalid 402 Maximum value is Invalid
Queries resulting in errors are not counted in the monthly query allowances.