A 509-status message means the traffic generated by the website exceeds the monthly allowance set by the hosting company. It is usually shown by a server when the traffic or data-transfer limit for a specific website has been reached.
Web-page hosts are companies that provide space on a server, usually in a data center, so that websites can be accessed on the Internet by the public. These companies provide web-hosting plans which have an associated traffic limit or data-transfer limit, usually calculated monthly in gigabytes. As the popularity of a website increases, so does the traffic it generates on a server.