503 Error Code Explained
The server is currently unavailable, because it is overloaded or down for maintenance.Generally, this is a temporary state.
Why it occurs
This is most often seen on extremely busy servers, and it indicates that the server was unable to complete the request due to a server overload.
Fixing 503 error code
The Web server is effectively 'closed for repair'. It is still functioning minimally because it can at least respond with a 503 status code, but full service is impossible.
If you are registered with 100pulse, your site will be monitored and you will be intimated by an email or a short message service when 503 status code error occurs.