gistfile1.js

    // Site 404
    app.use(function(req, res, next) {
      res.status(404)

      if (req.accepts('html')) {
        res.type('html')
        res.render('404', {
          url: req.get('host') + req.url,
          user: req.user,
          version: version
        })
        return
      }

      if (req.accepts('json')) {
        res.type('json')
        res.json({ error: '404: Not found' })
        return
      }

      res.type('txt')
      res.send('404: Not found')
    })