About behaviors conventions

Behaviors are prewritten ActionScript 2.0 code snippets that you can add to parts of a FLA file. Many developers enter ActionScript code either into one or several frames on the main Timeline or in external ActionScript files. However, when you use behaviors, sometimes code is placed directly on symbol instances (such as buttons, movie clips, or components) instead of being placed on the timeline.

Behaviors are not supported by ActionScript 3.0.