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) {
		menu_introduction_over = newImage("../images/menu_introduction-over.gif");
		menu_infomation_over = newImage("../images/menu_infomation-over.gif");
		menu_bill_over = newImage("../images/menu_bill-over.gif");
		menu_column_over = newImage("../images/menu_column-over.gif");
		menu_adaption_over = newImage("../images/menu_adaption-over.gif");
		menu_link_over = newImage("../images/menu_link-over.gif");
		menu_about_over = newImage("../images/menu_about-over.gif");
		preloadFlag = true;
	}
}