Update:  Currently i visit my app at domain.com:3000, but i would like to visit domain.com to see my app
I have setup nginx at 80 to proxy my rails app at 3000. below is the configuration
upstream railsapp {
  server 127.0.0.1:3000;
}
server {
  listen 80;
  server_name APP;
  # Tell Nginx and Passenger where your app's 'public' directory is
  root /var/www/APP/current/public;
  index index.html index.htm;
  # Static assets are served from the mentioned root directory
location / {
    root /var/www/APP/current;
    index index.html index.htm;
    proxy_pass http://railsapp/;
    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 Host $http_host;
    # proxy_set_header X-Real-Port $server_port;
    # proxy_set_header X-Real-Scheme $scheme;
    proxy_set_header X-NginX-Proxy true;
}
  # Turn on Passenger
  passenger_enabled on;
  passenger_ruby /usr/local/rvm/gems/ruby-2.1.3/wrappers/ruby;
}
i referred to : https://stackoverflow.com/a/5015178/1124639
this is located at /etc/nginx/sites-enabled/APP.conf and is included in /etc/nginx/nginx.conf as below within http{...}
include /etc/nginx/sites-enabled/*;
but my APP.com still shows 'Welcome to nginx on Ubuntu!' and APP.com:3000 shows my app. What am i doing wrong?
What i am using: 
Ubuntu 14.04 ec2 instance
nginx 1.8.0
unicorn server at 3000
 
    