Thanks for the helps!
With the Debugger i have discovered that the hotspot is not made well,intead it made me:
TypeError: Error #1009: Impossibile accedere a una proprietà o a un metodo di un riferimento oggetto null.
at Waterfall_fla::MainTimeline/init()
at Waterfall_fla::MainTimeline/frame1()
I'm a beginner in the flash's world, and i don't know how i can resolve the problem,btw i don't want to annoying you with stupid questions...
But if is interesting for you,i have taken the waterfall's file here:
http://www.flashandmath.com/flashcs4/waterfall/
Here you can find the zip file,and into it,the .fla file...
maybe sameone want to resolve it... ;)