When a toggle key, such as the Visible option in the Layer Settings dialog box, is used to toggle the visibility of a layer on and off, the portion of the Timeline palette where the layer is hidden is shaded red, as shown in Figure 17.16. This is to provide a visual reference to the area where the layer objects will not be visible.
Note
Keys can still be added to the shaded area where the layer contents are hidden, but the changes aren’t visible.