Getting 'error' response when adding my user profile to the url

var fs = require("fs");

function view(templateName, values, response) {
  // Read from template file
  var fileContents = fs.readFileSync('./views/' + templateName + '.html');
  //insert values in content

  //write out contents to response
  response.write(fileContents);

}

module.exports.view = view;

var Profile = require("./profile.js");
var renderer = require("./renderer.js");

// Handle HTTP route GET / and Post / i.e. Home
function home(request, response) {
  // if url == "/" && GET
  if (request.url === '/') {

    //show search
    response.writeHead(200, {'Content-Type': 'text/plain'});
    renderer.view("header", {}, response);
    renderer.view("search", {}, response);
    renderer.view("footer", {}, response);
    response.end();
  }

}

// Handle HTTP route GET / :username i.e. /benfarnham
function user(request, response) {
  //if url == "/...."
  var username = request.url.replace("/", "");
  if (username.length > 0) {
    response.writeHead(200, {'Content-Type': 'text/plain'});
    renderer.view("header", {}, response);

    //get json from treehouse
    var studentProfile = new Profile(username);
    //on "end"
    studentProfile.on("end", function(profileJSON){
      //show profile

      //Store the values we need
      var values = {
        avatarURL: profileJSON.gravatar_url,
        username: profileJSON.profile_name,
        badges: profileJSON.badges.length,
        javascript: profileJSON.points.JavaScript
      }

      //Simple response
      renderer.view("profile", values, response);
      renderer.view("footer", {}, response);
      response.end();

    });

    //on "error"
    studentProfile.on("error", function(error){
      //show error
      renderer.view("error", {errorMessage: error.message}, response);
      renderer.view("search", {}, response);
      renderer.view("footer", {}, response);
      response.end();
    });

  }
}

// Export routes

module.exports.home = home;
module.exports.user = user;

var router = require("./router.js");

var http = require('http');
http.createServer(function(request, response){
  router.home(request, response);
  router.user(request, response);
}).listen(3000);
console.log('Server running at http://<workspace-url>/');