function moveMenu () {
    if(!document.getElementById) return;
    var obj = document.getElementById("menu_box");
    var y = scrollTop() + 150;
    obj.style.top = y + "px";
    setTimeout("moveMenu();", 100);
}

function scrollTop () {
    if(window.pageYOffset)
        return window.pageYOffset;
    if(document.compatMode == "CSS1Compat")
        return document.body.parentNode.scrollTop;
    if(document.body.scrollTop)
        return document.body.scrollTop;
    return 0;
}