Changes

Different pars parts of a web page can sometimes be painted into intermediate surfaces retained by layers. It can be convenient to think of layers as the layers in image manipulation programs like The Gimp or Photoshop. Layers are organized as a tree. Layers are primarily used to minimize invalidating and repainting when elements are being animated independently of one another in a way that can be optimized using layers (e.g. opacity or transform animations), and to enable some effects (such as transparency and 3D transforms).