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) {
                navigation_01_over = newImage("nav/navigation_01_over.gif");
                navigation_02_over = newImage("nav/navigation_02_over.gif");
                navigation_03_over = newImage("nav/navigation_03_over.gif");
                navigation_04_over = newImage("nav/navigation_04_over.gif");
                navigation_05_over = newImage("nav/navigation_05_over.gif");
                navigation_06_over = newImage("nav/navigation_06_over.gif");
                preloadFlag = true;
        }
}