As another comment mentioned, frames were originally a proprietary Netscape feature and required special attention to make accessible to any other browser (usin

As another comment mentioned, frames were originally a proprietary Netscape feature and required special attention to make accessible to any other browser (using the noframes tag and providing links to the framed content, for example). Otherwise, users would just see an empty page (or, worse, a “best viewed with Netscape” message.) Before IE, there were at least two smaller browser “skirmishes”, and this was one of them. One before it was with Mosaic and inline image support, which most browsers did not have at the time (only links to view/download.)