[shiomiru]

Notably though, in 1997 Netscape 4 already had document.layers and IE4 document.all, two incompatible precursors to the DOM.

Some info about the LAYER API (which Netscape eventually killed, as the MS/W3C DOM prevailed):

http://web.archive.org/web/19971015223701/http://developer.n...

Also, a DOM compatibility guide can be found here:

http://www.dannyg.com/dl/JSB4RefPoster.pdf