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) {
		nav_top_over = newImage("images/nav_top_over.jpg");
		nav_tokutyou_over = newImage("images/nav_tokutyou_over.jpg");
		nav_naiyou_over = newImage("images/nav_naiyou_over.jpg");
		nav_tejun_over = newImage("images/nav_tejun_over.jpg");
		nav_musikomi_over = newImage("images/nav_mousikomi_over.jpg");
		nav_toiawase_over = newImage("images/nav_toiawase_over.jpg");
		nav_agree_over = newImage("images/mousikomi/nav_agree_over.jpg");
		nav_disagree_over = newImage("images/mousikomi/nav_disagree_over.jpg");
		preloadFlag = true;
	}
}