var winPopUp;
function openWindow(url,width,height,settings) {
	var leftPosition, topPosition;
	if(width == undefined) var width=500;
	if(height == undefined) var height=400;
	if(settings == undefined) var settings; 
	leftPosition = (screen.width)? (screen.width)/2 - (width/2): 0;
	topPosition = (screen.height)? (screen.height)/2 - (height/2): 0;
	if (settings == null) {
		settings = 'toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=yes,resizable=yes,copyhistory=no,width=';
		settings += width + ',height=' + height + ',top=' + topPosition + ',left=' + leftPosition;
	}
	if (winPopUp && !winPopUp.closed) {
		winPopUp.close();
	}
	winPopUp = window.open(url,'winPopUp',settings);
}