// open popup window
function popupWindow(url,winName,w,h) {
	leftPos = (screen.width) ? (screen.availWidth - w) / 2 : 0;
	topPos = (screen.height) ? (screen.availHeight - h) / 2 : 0;
	features = 'width='+w+',height='+h+',left='+leftPos+',top='+topPos+',status=0,menubars=0,scrollbars=0,resizable=0';
	winName = window.open(url,winName,features);
	if (window.focus) {
		winName.focus();
	}
}