nginx.conf

upstream my_upstream { #this line starts the list of real resources that exist behind the nginx server
  server 127.0.0.1:1337; 
  server 127.0.0.1:1338; #these servers are used in the order they are defined, in round robin fashion. there's more ways of load balancing in the docs
  server 127.0.0.1:1339 backup; #amazingness no.1, the keyword "backup" means that this server should only be used when the rest are non-responsive
  keepalive 64;
}

server {
    listen 80; 
    location /resource.html { #in my example the server only responds to requests for the file /request.html
      proxy_redirect off;
      proxy_set_header   X-Real-IP            $remote_addr;
      proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;
      proxy_set_header   X-Forwarded-Proto $scheme;
      proxy_set_header   Host                   $http_host;
      proxy_set_header   X-NginX-Proxy    true;
      proxy_set_header   Connection "";
      proxy_http_version 1.1;
      proxy_pass         http://my_upstream; #this sets the name of the server list that will actually process the request
      proxy_intercept_errors on; #amazingness no.2 if all of the proxied servers are down, this will return a 50x error (bad gateway) with this line we tell nginx to intercept this error instead of giving it back to the user
      error_page   502 503 504 =200 http://failoverhost.com/resource.html #in combination with the line above, if a 50x error exists nginx will redirect to the example host that can server the static content
    }
}