Nginx – How to Configure Global Error Page

Firstly, set your root directive outside the location block - in this case, above the error_page - directive. See the nginx pitfalls page. The reason for this is that many directives (including error_page) need to know paths relative to something - and all paths are assumed to be relative (i.e. /404.html is not in the root of your file system - it is relative to your document root).

server{
    #listen 80; - not needed
    server_name www.foo.com;
    root    /srv/www/foo/public_html;
    expires     1M;
    access_log  /srv/www/foo/logs/access.log;
    error_log   /srv/www/foo/logs/error.log;

    error_page 404 /404.html;

    location / {
        index   index.html;
        rewrite ^/(.*)/$ /$1 permanent;
        try_files "${uri}.html" $uri $uri/ =404;
    }

    location = /404.html {
        internal;
    }       
}

If the above does not resolve your error, increase the verbosity of your error_log (e.g. to 'info') and see what page nginx is actually serving when you hit a 404.

Use the magic of an include directive to specify all the necessary boilerplate, then just include /etc/nginx/standard-error-pages.conf in each vhost (make it part of the standard vhost template in your config management system). This also makes it real easy to override the error pages for a specific vhost (by not putting the include into that vhost config).