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_over = newImage("images/btn_home-over.gif");
		btn_sd_over = newImage("images/btn_sd-over.gif");
		btn_itc_over = newImage("images/btn_itc-over.gif");
		btn_tw_over = newImage("images/btn_tw-over.gif");
		btn_pm_over = newImage("images/btn_pm-over.gif");
		btn_about_over = newImage("images/btn_about-over.gif");
		btn_contact_over = newImage("images/btn_contact-over.gif");
		preloadFlag = true;
	}
}