Returns an array of all Navigator 4-only layer element objects in the current document. Also included in the array are references to other HTML elements with style sheets that set the element to be relative- or absolute-positioned (in which case, Navigator 4 treats those elements as layer objects). Items in this array are indexed (zero-based) in source code order, and may be accessed by number or by string name. As a dead-end feature implemented only in Navigator 4, the presence of this property indicates support for the unique referencing requirements for Netscape layers.