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) {
		home_over = newImage("images/navi/home-over.gif");
		couse_over = newImage("images/navi/couse-over.gif");
		ryoukin_over = newImage("images/navi/ryoukin-over.gif");
		sisutem_over = newImage("images/navi/sisutem-over.gif");
		pro_over = newImage("images/navi/pro-over.gif");
		map_over = newImage("images/navi/map-over.gif");
		otoiawase_over = newImage("images/navi/otoiawase-over.gif");
		preloadFlag = true;
	}
}