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) {
		conference_pc_over = newImage("images/top_nav/conference-pc_over.jpg");
		conference_over = newImage("images/top_nav/conference-over.jpg");
		pc_camp_over = newImage("images/top_nav/pc-camp_over.jpg");
		pc_over = newImage("images/top_nav/pc-over.jpg");
		camp_over = newImage("images/top_nav/camp-over.jpg");
		camp_pc_over = newImage("images/top_nav/camp-pc_over.jpg");
		preloadFlag = true;
	}
}