Set up a sub domain on a Nginx server Ubuntu 12.04

I am trying to learn as I go:

I have set up Nginx server on my Ubuntu 12.04 Droplet. I have successfully pointed my domain (registered @ godaddy) to my droplet (I can see the example page I created). Now I wanted to create a sub domain on the same server.

I created my config file:

cp /etc/nginx/available-sites/default /etc/nginx/available-sites/mydomain.com

and linked it in sites-enabled

in /etc/nginx/available-sites/mydomain.com I used the default code and pointed it to mydomain.com and to the folder containing the site, and like I said that works fine.

now I have tried to add to that same config file, before my main server class a new server class shown here:

server {
    listen 80;

    server_name dev.mydomain.com;
    location / {
            root /home/myusrnm/sites/site-drectory;
    }
}

I know very basic but I am trying to build as I go.

then in godaddy I added dev to my A record and pointed it to my droplet’s IP (which is the same as mydomain.com).

I have ping mydomain.com, and ping dev.mydomain.com, and everything is fine. My Nginx server restarted fine as well. It’s been about an hour and I still can’t point my browser to dev.mydomain.com. Do I have to set something up on the Digital Ocean DNS? or what am I missing?