The Adobe Flex 2 Language ReferenceActionScript 3.0 Language and Components Reference contains these appendices:

 Compiler ErrorsList and explanations of compiler error codes.
 Compiler WarningsList and explanations of compiler warning codes.
 Run-Time ErrorsList and explanations of run time error messages.
 ActionScript 2.0 MigrationList of differences between ActionScript 2.0 and 3.0.
 Character Set CodesList of character set definitions supported by Flash Player.
 What's NewList of recent changes in the ActionScript APIs.