These errors appear if there are configuration problems, for example, if the custom error page referenced is missing.
Log level set to INFO:
ROUTxxxx: Non Idempotent Request <Request-URL> cannot be retried
For example: ROUTxxxx: Non Idempotent Request http://sun.com/addToDB?x=11&abc=2 cannot be retried
Log level set to FINE:
RNTMxxxx: Invalid / Missing Custom error-url / page: <error-url> for web-module: <web-module>
For example: RNTMxxxx: Invalid / Missing Custom error-url / page: myerror1xyz for web-module: test