Mozilla Error Lookup

The Mozilla Error Lookup page has an up-to-date list of all the result codes defined within the Mozilla, Firefox, Thunderbird and SeaMonkey source code. Each result code - even if it is not defined in the source - will be split in to a module, severity and number using the XPConnect result code rules. Usually, though, the code will be defined and have a symbolic name (the name used within the code itself).