Airport code data source ?

Sometimes an airport code at world-airport-codes dot com is not found. E.g., EDDF or DDF truns out no results for the airport code.
Any other website out there ?

List of ICAO airport codes (ICAO airport codes are used in FlightAware)

list of IATA airport codes

Many thanks again, you rock. Guess you are the type who help peopel in need. This place must be so popular because of users like you, otherwise in this kind of maze, its easy for someone like me to get gobbled up by so much out here and not return again for all the seeming confusion that may overwhelm a new comer.