This is an element created by Netscape that allows an author to define precisely positioned 2-dimensional layout consisting of overlapping layers of transparent or solid content on a web page.
Layers can have a stacking order that allows a virtual third z-dimension to be defined.
Using this, layers can appear on top of other layers. Layers can be nested and moved in a dynamic fashion via scripting. It overrides the default behavior of placing new layers on top of all existing layers. References to layers not yet defined result in default layer creation behavior - i.e. the new layer will be placed on top of all existing layers. An existing valid alphanumeric layer NAME value.