/*function findPos(obj) {
    var curleft = curtop = 0;
    if (obj.offsetParent) {
        do {
            curleft += obj.offsetLeft;
            curtop += obj.offsetTop;
        } while (obj = obj.offsetParent);
    }
    return [curleft,curtop];
}*/

function mark(posx, posy) {
    var marker = document.getElementById('marker');
    marker.style.left    = (posx - 25) + "px";
    marker.style.top     = (posy - 25) + "px";
    marker.style.display = "block";
}

function unmark() {
    document.getElementById('marker').style.display = "none";
}