function newImage(arg) {
    if (document.images) {
        rslt = new Image();
        rslt.src = arg;
        return rslt;
    }
}

function changeImages() {
    if (document.images && (preloadFlag == true)) {
        for (var i = 0; i < changeImages.arguments.length; i += 2) {
            document[changeImages.arguments[i]].src = changeImages.arguments[i + 1];
        }
    }
}

var preloadFlag = false;
function preloadImages() {
    if (document.images) {
        nav1_over = newImage("images/nav/nav1_over.gif");
        nav2_over = newImage("images/nav/nav2_over.gif");
        nav3_over = newImage("images/nav/nav3_over.gif");
        nav4_over = newImage("images/nav/nav4_over.gif");
        nav5_over = newImage("images/nav/nav5_over.gif");
        nav6_over = newImage("images/nav/nav6_over.gif");
        nav7_over = newImage("images/nav/nav7_over.gif");
        nav8_over = newImage("images/nav/nav8_over.gif");
        nav9_over = newImage("images/nav/nav9_over.gif");
        nav10_over = newImage("images/nav/nav10_over.gif");
        nav11_over = newImage("images/nav/nav11_over.gif");
        nav12_over = newImage("images/nav/nav12_over.gif");
        nav13_over = newImage("images/nav/nav13_over.gif");
        nav14_over = newImage("images/nav/nav14_over.gif");
        nav15_over = newImage("images/nav/nav15_over.gif");
        nav16_over = newImage("images/nav/nav16_over.gif");
        nav17_over = newImage("images/nav/nav17_over.gif");
        preloadFlag = true;
    }
}