The tag <DIV> </DIV> creates a division, a block within a document that can be treated as a single object. The tag <LAYER> </LAYER> creates a layer for the same purpose.
Only NC4 uses LAYER at this time. Both NC4 and IE4 use divisions, with some subtle differences. In NC4 the DIV does not have any events, while in IE4 it has a full set. This keeps NC4 from executing code designed using DIV events.
IE4 will NOT properly display pages illustrating LAYER!