Return JSON for 404 error instead of html

Tue May 13 04:08:59 UTC 2014

How can I return a custom JSON body on 404, instead of the default html of:

<html>

    <head>
        <title>404 Not Found</title>
    </head>

    <body bgcolor="white">
        <center>
            <h1>404 Not Found</h1>
        </center>
        <hr>
        <center>nginx</center>
    </body>

</html>

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,250033,250033#msg-250033