Cannot GET / Nodejs Error

I think you're missing your routes, you need to define at least one route for example '/' to index.

e.g.

app.get('/', function (req, res) {
  res.render('index', {});
});

Much like leonardocsouza, I had the same problem. To clarify a bit, this is what my folder structure looked like when I ran node server.js

node_modules/
app/
  index.html
  server.js

After printing out the __dirname path, I realized that the __dirname path was where my server was running (app/).

So, the answer to your question is this:

If your server.js file is in the same folder as the files you are trying to render, then

app.use( express.static( path.join( application_root, 'site') ) );

should actually be

app.use(express.static(application_root));

---

The only time you would want to use the original syntax that you had would be if you had a folder tree like so:

app/
  index.html
node_modules
server.js

where index.html is in the app/ directory, whereas server.js is in the root directory (i.e. the same level as the app/ directory).

Side note: Intead of calling the path utility, you can use the syntax application_root + 'site' to join a path.

Overall, your code could look like:

// Module dependencies.
var application_root = __dirname,
express = require( 'express' ), //Web framework
mongoose = require( 'mongoose' ); //MongoDB integration

//Create server
var app = express();

// Configure server
app.configure( function() {

    //Don't change anything here...

    //Where to serve static content
    app.use( express.static( application_root ) );

    //Nothing changes here either...
});

//Start server --- No changes made here
var port = 5000;
app.listen( port, function() {
    console.log( 'Express server listening on port %d in %s mode', port, app.settings.env );
});

Have you checked your folder structure? It seems to me like Express can't find your root directory, which should be a a folder named "site" right under your default directory. Here is how it should look like, according to the tutorial:

node_modules/
  .bin/
  express/
  mongoose/
  path/
site/
  css/
  img/
  js/
  index.html
package.json

For example on my machine, I started getting the same error as you when I renamed my "site" folder as something else. So I would suggest you check that you have the index.html page inside a "site" folder that sits on the same path as your server.js file.

Hope that helps!