function open_window(url_link, window_name, window_width, window_height)
{
	//window_height = screen.height;
	screen_width = screen.width;
	screen_height = screen.height;
	
	if (window_height == "" || window_height == "0")
	{
		window_height = screen_height - 100;
	}
	
	if (window_width == "" || window_width == "0")
	{
		window_width = 700;
	}
	
	position_top = (screen_height - window_height - 50) / 2;
	position_left = (screen_width - 10 - window_width) / 2;

	window_options = 'toolbar=0,scrollbars=no,location=0,statusbar=0,menubar=0,resizable=0,width=' + window_width + ',height=' + window_height + ',left=' + position_left + ',top=' + position_top + ',leftmargin=0';
	window.open(url_link, window_name, window_options);
}