It seems that no matter where the play/read head is, when a new element is added to the stage (and a new layer is created) the element is always visible from the start of the animation. I know this isn't Flash, but can you add elements to the animation that only begin their life say, at T=00:03? Do you have to use the CSS Usability keyframe to hide it until you want its face to show (or something like that)?
Hi Roy, if you have objects on the Stage, they will be visible, unless you either set a keyframe for the "alpha" to 0, or turn the "display" property to "off". Bother properties are available when you set keyframes for an object. When you later want to show the object, set a new keyframe for "alpha" to 100, or "display" to "on".
You can also dynamically pull objects from the library, and add them to the stage whenever you want, but that is a bit more advanced.