server {
 listen 80;
 server_name localhost;

 error_page 404 /custom.html;

 location /{
   root /usr/share/nginx/html;
   index    index.html index.htm;
   include  /etc/nginx/mime.types;
 }

location /custom.html{
   root /usr/share/nginx/html;
   index    index.html index.htm;
   include  /etc/nginx/mime.types;
   try_files $uri $uri/ /index.html;
 }
}