In a layer, Flash stacks objects in the order in which they are created, placing the most recently created object at the top of the stack. The stacking order of objects determines how they appear when they overlap. You can change the stacking order of objects at any time.
Drawn lines and shapes always appear below groups and symbols on the stack. To move them up the stack, you must group them or make them into symbols.
Layers also affect the stacking order. Everything on Layer 2 appears in front of everything on Layer 1, and so on. To change the order of layers, drag the layer name in the Timeline to a new position.