window.onload = function () {
    PreloadImages();
}

function PreloadImages() {
    var urls = new Array();
    urls.push("/Images/menu_hover2.png");
    urls.push("/Images/dot.png");

    for (var i = 0; i < urls.length; i++) {
        var img = new Image();
        img.src = urls[i];
    }
}