There are a number of ways. It would depend on the page and the menu. I would try:
getting a reference to the iframe as an element and firing its focus() function.
Or:
setting a hash that references a named anchor at the bottom of the page.
Or:
scrolling the window by a large amount.
In the first scenario you can get a reference to the iframe if it has an id as:
document.getElementById('frame_id').focus();
where frame_id is the id attribute of the iframe. Or if it has a name:
document.getElementsByName('frame_name')[0].focus();
where frame_name is the name attribute of the iframe.
In the second scenario, put a named anchor at the bottom of the page:
<a name="bottom"></a>
Then use this code to to seek the page to it:
window.location.hash = '#bottom';
In the third scenario, just do:
window.scrollBy(0, 100000);
If you want more help, please include a link to the page on your site that contains the problematic code so we can check it out.