Drop shadow transparency

i put a drop shadow on my picture and save it(i use photoshop).then i import the pictre(with the drop shadow)into flash.but what i found is the shadow is not ‘transparent’ when i export the swf,i mean i can’t see through the shadow.can somebody pls help?

Make sure that the fill opacity on the layer with the dropshadow is at 0%. And save it as a PNG or GIF.

use .png24 as the format, make sure you turn off matte and use alpha transparency in the export settings

yeah its gotta be png