Nginx - Customizing 404 page

You use the error_page property in the nginx config.

For example, if you intend to set the 404 error page to /404.html, use

error_page 404 /404.html;

Setting the 500 error page to /500.html is just as easy as:

error_page 500 /500.html;

You can setup a custom error page for every location block in your nginx.conf, or a global error page for the site as a whole.

To redirect to a simple 404 not found page for a specific location:

location /my_blog {
    error_page    404 /blog_article_not_found.html;
}

A site wide 404 page:

server {
    listen 80;
    error_page  404  /website_page_not_found.html;
    ...

You can append standard error codes together to have a single page for several types of errors:

location /my_blog {
    error_page 500 502 503 504 /server_error.html
}

To redirect to a totally different server, assuming you had an upstream server named server2 defined in your http section:

upstream server2 {
    server 10.0.0.1:80;
}
server {
    location /my_blog {
        error_page    404 @try_server2;
    }
    location @try_server2 {
        proxy_pass http://server2;
    }

The manual can give you more details, or you can search google for the terms nginx.conf and error_page for real life examples on the web.