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("img/navigation_01-over.jpg");
navigation_02_over = newImage("img/navigation_02-over.jpg");
navigation_03_navigation_01_over = newImage("img/navigation_03-navigation_01.jpg");
preloadFlag = true;
}
}