I guess you have your frameset something like this:
<frameset rows="100,*,80">
<frame src="f1.htm"/>
<frameset cols="120,*">
<frame src="left.htm"/>
<frame src="right.htm"/>
</frameset>
<frame src="f2.htm"/>
</frameset>
Which will look something like this:
________________________
| f1.htm |
|______________________|
| | |
| left.htm | right.htm |
|__________|___________|
| f2.htm |
|______________________|
If you want the left.htm to fill the entire height in the window, you need to re-structure to this:
<frameset cols ="120,*">
<frame src="left.htm"/>
<frameset rows="100,*,80">
<frame src="f1.htm"/>
<frame src="right.htm"/>
<frame src="f2.htm"/>
</frameset>
</frameset>
Which will look something like this:
________________________
| | f1.htm |
| |___________|
| left.htm | |
| | right.htm |
| |___________|
| | f2.htm |
|__________|___________|