js_get_elementTop()

/**
* Gets the vertical position of an element.
*
* Credit: http://www.aspandjavascript.co.uk/javascript/javascript_api/get_element_top_left.asp
*/
function js_get_elementTop(elem) {

yPos = elem.offsetTop;
tempEl = elem.offsetParent;
while (tempEl != null) {
yPos += tempEl.offsetTop;
tempEl = tempEl.offsetParent;
}
return yPos;
}