Internet users must already know about “Error 404” code, which is a code that shows up every time a web page is not available to be accessed. But this code does not explain why the page cannot be accessed. So, Internet Engineering Steering Group (IESG) agreed to make a new status, that is HTTP 451 Unavailable for Legal Reasons. If this code shows on your page, it means the page has law problem. For example, the content of the website is violating the nation’s security, copyright, and insult laws.
This HTTP 451 code also indicates a possibility that the accessed server is not the original one. The number 451 itself is taken from Ray Bradbury’s novel called Fahrenheit 451, which tells about a ban of the publication of books. Actually this code had been already submitted since 2013, but IESG had just approved on December 18, 2015. But until now, this code has not started to operate yet until further notice.