Splitting an existing frame creates a new frameset inside the current frameset file. A frameset that contains another frameset is called a parent frameset.

To create a nested frameset:

1	Place the cursor within an existing frame.
2	Choose Modify > Frameset > Split Frame Up, Down, Left, or Right.

You can also Alt-drag (Windows) or Option-drag (Macintosh) a frame border into the Document window to split the frame vertically or horizontally.

To view the frameset HTML code, select a frameset by clicking on a frameset border and then open the HTML inspector. The code looks something like this:

<frameset cols="207,397">
  <frame src="file:///C|/SITEROOT/UntitledFrame-2" name="Frame One">
  <frameset rows="270,268">
    <frame src="file:///C|/SITEROOT/UntitledFrame-3" name="Top Right">
    <frame src="/temp.htm" name="Top Left"> 
  </frameset> 
</frameset>

You can see how the new frameset is indented within the parent frameset.