FlashFirebug is a Firefox extension that allows developers to debug any Flash on any webpage, inspect display list, change properties on the fly and see the warnings, errors and traces directly in the extension. The main purpose of FlashFirebug is to make Flash debugging as easy as HTML and javascript debugging with an interface derived from Firebug and familiar to developers.
Debugging other people’s SWF files may help you understand how they work.
https://addons.mozilla.org/en-US/firefox/addon/flashfirebug/
