用JS的方式获取就要用getBoundingClientRect方法，like this:

window.frames['mainframe'].document.getElementById('Img').getBoundingClientRect().left;

 

但是JS时灵时不灵，下面就是不用JS的方法：

public Point GetOffset(HtmlElement el){    //get element pos    Point pos = new Point(el.OffsetRectangle.Left, el.OffsetRectangle.Top);    //get the parents pos    HtmlElement tempEl = el.OffsetParent;    while (tempEl != null)    {        pos.X += tempEl.OffsetRectangle.Left;        pos.Y += tempEl.OffsetRectangle.Top;        tempEl = tempEl.OffsetParent;    }    return pos;}var point = GetOffset(element);var x = point.X;var y = point.Y;