function GetScreenMargin(screen, popup){
	if(popup > screen) return 0;
	margin = screen - popup;
	margin = margin/2;
	margin = Math.round(margin);
	return margin;
}

function ShowPopup(path, width, height, name, scroll, add_param){
	if(scroll == 'undefined') scroll = 'no';
	margin_left = GetScreenMargin(self.screen.width, width);
	margin_top = GetScreenMargin(self.screen.height, height);
	param = 'left=' + margin_left + ',top=' + margin_top + ',width=' + width + ',height=' + height + ',menubar=no,scrollbars=' + scroll + ',status=no';
	if(add_param != 'undefined') param += add_param;
	window.open(path, name, param);
}