The <FRAMESET> tag does all the dividing. That's all it does... divide up windows. It specifies a few things regarding how to divide them up, but remember, whenever you want to do some dividing - use <FRAMESET>.
Can we divide it into more than 2 pieces? Yes, just make sure that you specify a page for each section or the browser's gonna get confused.
VIEW ITIMPORTANT NOTE: Whenever you make a change to your document, just save it, then hit the Refresh/Reload button on your browser. In many instances just hitting the refresh button doesn't quite do the trick. In that case...
Internet Explorer users: Click Refresh while holding down the CTRL key.
Netscape users: Click Reload while holding down the SHIFT key.
It's pretty obvious that we can make the frames all differents sizes. Just make sure your arithmetic is correct or the browser will come up with its own interpretation.