Flash CS3 Tutorial
How to Hide a Flash Layer
Hiding a layer turns off the visibility for the layer. It is particularly handy while you are working with several layers of content.
The content for the hidden layer becomes visible once the swf file is made.
Make sure the timeline/layers panel is open by choosing Window > Timeline.
Add a rectangular object to the workspace with the Rectangle tool (r key).
Click the layer dot below the eye icon to hide the layer.
Test your movie (Control > Test Movie) (Cmd/Return (PC-Ctrl/Enter) to view the animation. The rectangle should appear once you create the swf file.