The 503 Service Unavailable error is an HTTP status code that means the server/site is simply not available at the moment or is overloading.

HTTP Error 503 Definition: The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay MAY be indicated in a Retry-After header. If no Retry-After is given, the client SHOULD handle the response as it would for a 500 response.

HTTP Error 503 Messages

• 503 -  Service Unavailable
• 503 – Service Temporarily Unavailable
• HTTP Error 503 – Service Unavailable