How to create a fading, square transition effect in Flash. View Effect.
To start off, create a new Flash document with the following settings.
We're going to use 3 images in this tutorial, sized 720x174. Import the 1st image into flash
Convert the image into an MC called allImages. Click "Export for Actionscript", which will give it an identifier of the same name as the MC. This identifier is needed so that many instances of the the MC can be created, using Actionscript.