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 terns nginx.conf and error_page for real life examples on the web.