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_home_home_over = newImage("images/index/btn_home_home-over.gif");
		btn_issues_home_over = newImage("images/index/btn_issues_home-over.gif");
		btn_teachers_home_over = newImage("images/index/btn_teachers_home-over.gif");
		btn_calendar_home_over = newImage("images/index/btn_calendar_home-over.gif");
		btn_subscript_home_over = newImage("images/index/btn_subscript_home-over.gif");
		btn_ngexp_home_over = newImage("images/index/btn_ngexp_home-over.gif");
		btn_readit_home_over = newImage("images/index/btn_readit_home-over.gif");
		btn_index_listen_over = newImage("images/index/btn_index_listen-over.jpg");
		btn_index_moreissue_over = newImage("images/index/btn_index_moreissue-over.gif");
		btn_index_milkcarton_over = newImage("images/index/btn_index_milkcarton-over.gif");
		preloadFlag = true;
	}
}