Click on a link to wipe out the currently visible layer and wipe in the selected one. Layers don't need to be the same size.

layer 1 | layer 2 | layer 3 | layer 4

This is layer 2. Your layers could be positioned anywhere. In this example they all have the same position.

This is layer 3. Opera just shows and hides the layers in this example since Opera can't do the wipes.