<script type="text/javascript">
document.getElementById("frame1").scrolling="yes";
function removeScrollbars()
document.getElementById("frame1").scrolling="no";
<iframe src="/example/hdom/frame_a.html" id="frame1" ></iframe>
<input type="button" onclick="addScrollbars()" value="Add Scrollbars" />
<input type="button" onclick="removeScrollbars()" value="Remove Scrollbars" />