The internet might be available worldwide, but varying legal systems in different countries often lead to sites being blocked or filtered for reasons that aren't always clear. A new internet error code aims to solve the lack of transparency associated with censorship and legal obstacles. If you're browsing the web today and reach a 404 error that typically means the page you were looking for wasn't found. A new 451 error code is designed to notify you that content has been blocked.

Tim Bray, a co-author of the XML specification, wants web developers to adopt error code 451 (a nod to Fahrenheit 451) to let websites warn you that you can't access a site or a piece of content for legal reasons. The Internet Engineering Steering Group (IESG) has approved the initial suggestion, allowing developers to start implementing it ahead of "a few more process bits," according to Mark Nottingham, chairman of the IETF HTTP Working Group.

When Bray originally submitted the draft for the status code more than three years ago, many sites were using the 403 forbidden status code to block The Pirate Bay in the UK following a court ruling. If implemented widely, Bray's new code should help prevent the confusion around blocked sites, but it's only optional and requires web developers to adopt it. "It is imaginable that certain legal authorities may wish to avoid transparency, and not only forbid access to certain resources, but also disclosure that the restriction exists," explains Bray.