Scrolling an iframe with JavaScript?

You can use the onload event to detect when the iframe has finished loading, and there you can use the scrollTo function on the contentWindow of the iframe, to scroll to a defined position of pixels, from left and top (x, y):

var myIframe = document.getElementById('iframe');
myIframe.onload = function () {
    myIframe.contentWindow.scrollTo(xcoord,ycoord);
}

You can check a working example here.

Note: This will work if both pages reside on the same domain.

Use the scrollTop property of the frame's content to set the content's vertical scroll-offset to a specific number of pixels (like 100):

<iframe src="foo.html" onload="this.contentWindow.document.documentElement.scrollTop=100"></iframe>

The main issue when programming the scroll is related to getting the whole document embedded into the page, remember than an Iframe would be a full-page (head and all) inside your main doc, for this reason, before actually scrolling, you need to get the inner document, not just the container, so you can actually scrollTo.

We add a validation to sendure compatibility, and the differences betwen contentDocument and windows can be found here

Havign this, the final code would be:

var $iframe = document.getElementByID('myIfreme');
var childDocument = iframe.contentDocument ? iframe.contentDocument : iframe.contentWindow.document;
 childDocument.documentElement.scrollTop = 0;