14 Jan 2015

451 unavailable: Campaign for a new error message

Anyone who uses the World Wide Web will be familiar with the ‘404 Page Not Found’ message which appears when you visit a webpage that doesn’t exist.

Many of us will also have seen the ‘403 Forbidden’ error message for denying access.

One campaign group in the UK is lobbying for a new message to be used on the web. They want a ‘451 Unavailable’ message to be displayed every time a webpage is blocked by a government.

Leading the campaign is the UK-based Open Rights Group, a free speech and digital consumer rights group. ‘451’ is a reference to the novel Fahrenheit 451, a dystopian novel by Ray Bradbury set in a future America where books are outlawed.

451 degrees Fahrenheit is reported to be the auto-ignition point of paper - the temperature at which it will catch fire without being exposed to an external flame. Governments are increasingly forcing Internet Service Providers to block websites.

The reasons vary, from copyright infringement and sexually offensive material to political motives. Trade union websites have been blocked by governments across the world.

Recently in the UK, the British Government has forced ISPs to apply a filter designed to block pornographic images by default, with users needing to opt out of the filters.  This recently came fully into force in December last year.

However, different ISPs have taken different approaches to implementing this, and many non-pornographic sites have been blocked by mistake. Often the ‘403 Forbidden’ message is displayed when accessing a blocked site.

The campaign argues that a new error message will make it clear that the content has been blocked. The Open Rights Group’s campaign is based on a proposal made in 2012 by Google engineer Tim Bray. He was the first to propose a need for a new error code, and submitted the new code for consideration by the Internet Engineering Task Force (IETF), the body that oversees web standards, such as 404 errors and http protocols.

The campaign calls for error 451 pages to:

“include all the key information about the blocking order including links to the relevant court order, how to challenge the block and the law allowing the court to block websites in that country."

It’s an interesting proposal, and would certainly help make it clear to users why they can’t access certain sites.  For more information about the campaign, visit

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