title: Position overlay div at % from top edge of browser not page top
body: <p>is there a way to position a floated overlay div say "20%" from the top edge of the users browser window - e.g. so not 20% from the top of the <code>&lt;body&gt;</code> tag - e.g. so that if user scrolls the page and clicks a link way down the page - the floated overlay div is nicely in view floated "20%" from the top edge of the browser?</p>