Assets/BallControl.js(9,9): BCE0144: 'UnityEngine.Component.rigidbody' is obsolete. Property rigidbo

Code (JavaScript):

1. #pragma strict
2.  
3. var rotationSpeed = 100;
4.  
5. function Update ()
6. {
7.     var rotation : float = Input.GetAxis ("Horizontal") * rotationSpeed;
8.     rotation *= Time.deltaTime;
9.     rigidbody.AddRelativeTorque (Vector3.back * rotation);
10. }

 

Your tutorial is a million years old. Find a more recent one.

 

how to fix errors :
Assets/BallControl.js(9,9): BCE0144: 'UnityEngine.Component.rigidbody' is obsolete. Property rigidbody has been deprecated. Use GetComponent<Rigidbody>() instead. (UnityUpgradable)

and
Assets/BallControl.js(9,19): BCE0019: 'AddRelativeTorque' is not a member of 'UnityEngine.Component'.
from the script above

 

The error message tells you what to do. As @Baste states, the tutorial you are following is very old. It isn't worth following it as it no only uses outdated APIs, it also uses the discontinued Unity script.

Go to https://unity.com/learn and follow a more recent tutorial.