The source code the the Math 489 home page uses frames. Here it is: 
<HTML>
<HEAD>
<TITLE>Math 489.500</TITLE>
</HEAD>

<frameset cols="30%, 70%, *">
	<frame src="class-toc.html" name="toc">
	<frame src="class-main.html" name="main">
	<frame src=applets.html name=applets>
</frameset>
</HTML>
The purpose of the <frameset> and the </frameset> commands are to group the various frame components. The <frameset> and the </frameset> commands can be nested!

The first argument to <frameset> is either rows= or cols= and gives the number of frames in that frameset. The argument which follows tells the dimension of the frames in terms of pixels (absolute width or height) or relative width or height (in terms of percentage of browser width or height). The special character "*" tells the browser to fit the remaining frame into the remaining space.

Note a frames dimension can be zero, but nothing can be shown in such a frame. Zero width/height frames are typically used as a target for popups.

The first argument to the <frame> command is the source of the frame contents (usually an .html file) and the second argument is the name of the frame. This is critical, since it provides something for the target to point to in the <a href=... target=...> command. Frame names are global, and can be used in any window descended from the file with the frame name defined in it.