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) {
		tac2_over = newImage("images/tac2-over.gif");
		tac3_over = newImage("images/tac3-over.gif");
		tac4_over = newImage("images/tac4-over.gif");
		tac5_over = newImage("images/tac5-over.gif");
		navi_sakakumo_over = newImage("images/navi-sakakumo-over.gif");
		navi_yoshifuru_over = newImage("images/navi-yoshifuru-over.gif");
		navi_saneyuki_over = newImage("images/navi-saneyuki-over.gif");
		navi_shiki_over = newImage("images/navi-shiki-over.gif");
		preloadFlag = true;
	}
}