Go to the WLS Admin console and see if the application status is New. If yes, you need to start the application and make sure it turned to Active status. Then you can browse your application.
1. Logon to Admin connsole:
http://localhost:7001/console [use the userId/Password you provided while creating the domain]
2. Click on the "deployments" link on the left side pane of the page
3. Check the box against your application and click on the start button (service all requests).
4. You should finally see the apllication in "Active" state once it is started successfully.
5. Now, browse your application
http://localhost:7001/HelloWorld/hello