function popUp(windowName, URLtoOpen, width, height)  {
	
	newWindow=window.open(URLtoOpen, windowName, 'height=' + height + ',width=' + width + ',scrollbars=yes,toolbar=no,status=no,directories=no');
	
	var left = (screen.availWidth/2 - width/2);
	var top = (screen.availHeight/2 - height/2);
	
	newWindow.moveTo(left, top);
	newWindow.focus();
}