var _move = false;
var _newTop = 20;
window.onscroll = function() {
    var scrollY = window.pageYOffset || document.body.scrollTop || document.documentElement.scrollTop;
    var _top = document.getElementById("sky_banner_div").offsetTop;
    _newTop = 20 + scrollY;
    
    if(!_move) {
        _move = true;
        
        if(_top > _newTop)
            moveUp();
        else
            moveDown();
    }
};

function moveUp() {
    var _top = document.getElementById("sky_banner_div").offsetTop;
    document.getElementById("sky_banner_div").style.top = (_top -7)+"px";

    if(document.getElementById("sky_banner_div").offsetTop > _newTop)
        window.setTimeout("moveUp();", 1);
    else {
        _move = false;
    }
}

function moveDown() {
    var _top = document.getElementById("sky_banner_div").offsetTop;
    document.getElementById("sky_banner_div").style.top = (_top +7)+"px";
    
    if(document.getElementById("sky_banner_div").offsetTop < _newTop)
        window.setTimeout("moveDown();", 1);
    else {
        _move = false;
    }
}