index.html
<html>1.html
<frameset cols="20%,80%">
<frame name="main" src="1.html">
<frameset cols="25%,75%">
<frame name="f1" src="1-1.html" />
<frame name="f2" src="1-2.html" />
</frameset>
</frameset><noframes></noframes>
</html>
<html>1-1.html
<body>
First Frame<br/>
<a href="1-1.html" target="f2">Second Frame</a>
<br/>
<a href="1-2.html" target="f1">Third Frame</a>
<br/>
</body>
</html>
<html>1-2.html
<body>
Third Frame
</body>
</html>
<html>
<body>
Second frame
</body>
</html>