When a web page shows you an “Internal Server Error”, the webserver also returns a 500 status code. It means there is something wrong on the website itself. The user requested a proper URL, but something on the server makes it unable to fulfil that request. The user has no way to resolve this except to wait for it to disappear. These errors are the responsibility of the website owner to handle and prevent.
One of our most basic features is to help you stay on top of errors like this on your pages. Read more on how to get notified about Internal Server Errors