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) {	
		center1_over = newImage("images/pics/presentation/professional.jpg");
		center2_over = newImage("images/pics/presentation/fabrication.jpg");
		center3_over = newImage("images/pics/presentation/boiler.jpg");
		center4_over = newImage("images/pics/presentation/process.jpg");
		center5_over = newImage("images/pics/presentation/air.jpg");
		center6_over = newImage("images/pics/presentation/commercial.jpg");
		center7_over = newImage("images/pics/presentation/distribution.jpg");
		center8_over = newImage("images/pics/presentation/hvac.jpg");
		preloadFlag = true;
	}
}