var newWin;

function centeredWindow(url,winname,w,h) {
	windowleft = (screen.width - w)/2;
	windowtop = (screen.height - h)/2;
	settings = '"toolbar=no, directories=no, menubar=no, scrollbars=yes, resizable=no, status=no, width='+w+', height='+h+', left='+windowleft+', top='+windowtop+'"';
	closeWindow();
	newWin = window.open(url,winname,settings);
	newWin.focus();
}
	
function closeWindow() {
	if (newWin && !newWin.closed) {
			newWin.close();
	}
}