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) {
		btn_kanto_over = newImage("../img/btn_kanto-over.png");
		btn_tamatebako_over = newImage("../img/btn_tamatebako-over.png");
		btn_koten_over = newImage("../img/btn_koten-over.png");
		btn_did_you_know_over = newImage("../img/btn_did_you_know-over.png");
		btn_essays_over = newImage("../img/btn_essays-over.png");
		btn_short_over = newImage("../img/btn_short-over.png");
		btn_tosho_over = newImage("../img/btn_tosho-over.png");
		btn_news_over = newImage("../img/btn_news-over.png");
		btn_contact_over = newImage("../img/btn_contact-over.png");
		btn_aisatsu_over = newImage("../img/btn_aisatsu-over.png");
		btn_shinyaku_over = newImage("../img/btn_shinyaku-over.png");
		btn_harada_over = newImage("../img/btn_harada-over.png");
		btn_henshu_over = newImage("../img/btn_henshu-over.png");
		preloadFlag = true;
	}
}