gistfile1.txt

    // custom error handler
    app.use(function (err, req, res, next) {
      if (err.message
        && (~err.message.indexOf('not found')
        || (~err.message.indexOf('Cast to ObjectId failed')))) {
        return next()
      }

      console.error(err.stack)
      res.status(500).render('500')
    })

    app.use(function (req, res, next) {
      res.status(404).render('404', { url: req.originalUrl })
    })

snippet from question http://stackoverflow.com/questions/18406591/expressjs-all-routes-are-404/18407658#18407658