bayden.com<br/>
<button onclick="alert(document.getElementById('frm1').contentWindow.length)">Count subframes of frame</button><br />
<iframe id="frm1" src="https://webdbg.com/test/frames/nest2.asp"></iframe>

<hr />
<iframe id="frm2" src="https://webdbg.com/test/frames/nest2.asp"></iframe>