There are seven main errors when it comes to website monitoring

• Unable to connect to server - The connection timeout results from this error. This is because the server that’s being pinged is down or Unreachable.
• DNS lookup problem - Incorrect spellings or domain names results in this error.
• Connection refused by the server -  Internal server issues or Overloaded web servers results in this error.
• Connection Timeout - Connection was established but the HTTP web page takes time to load and hence the connection timeout.
• Server Unavailable(503)  - The web server is currently unavailable to process the request.
• Internal Server Error(500) - The server reports an internal error.
• Bad Gateway(502) - Web server is down as a result of miscommunication between gateway and server.