What is wrong with this catapult script?

Hi can anyone help me please. I've got two errors with this particular script. The error messages are:

NullReferenceException CatapultMainScript.Start () (at Assets/Scripts For Project/CatapultMainScript.js:24)

NullReferenceException CatapultMainScript.Update () (at Assets/Scripts For Project/CatapultMainScript.js:33)

The script is:

var grenade : GameObject; var throwThis : int = 3200; var rotspeed : int = 10;

private var placeHolder : Transform; private var Launcher : Transform; private var target : GameObject; private var cRight : Transform; private var cLeft : Transform; private var firingForm : float; private var distance : float; private var originalPos : Vector3; private var originalRotation : Quaternion; private var originalThrow : int; private var originalDist : float;

function Start(){

 placeHolder = transform.Find("Catapult Base/Catapult Launcher/Holder");
 target = GameObject.Find("target");
 cRight = target.transform.Find("CubeR");
 cLeft = target.transform.Find("CubeL");
 Launcher = transform.Find("Catapult Base/Catapult Launcher");
 firingForm = Vector3.Distance(placeHolder.transform.position, target.transform.position);
 originalDist = firingForm;
 originalPos = target.transform.position;
 originalRotation = Launcher.transform.rotation;
 originalThrow = throwThis;

}

function Update(){

 placeHolder.transform.LookAt(target.transform);
 if(Input.GetAxis("Mouse X") > 0 && cRight.renderer.isVisible){
     Launcher.transform.Rotate(0, Time.deltaTime * (rotspeed * -1), 0);
     target.transform.Translate(Time.deltaTime * (rotspeed * 2), 0, 0);
     firingForm = Vector3.Distance(placeHolder.transform.position, target.transform.position);
 }

 if(Input.GetAxis("Mouse X") < 0 && cLeft.renderer.isVisible){
     Launcher.transform.Rotate(0, Time.deltaTime * rotspeed, 0);
     target.transform.Translate(Time.deltaTime * (rotspeed * 2) * -1, 0, 0);
 }

 if(Input.GetAxis("Mouse Y") > 0 && target.transform.position.z < 913){
     firingForm = Vector3.Distance(placeHolder.transform.position, target.transform.position);
     target.transform.Translate(0, 0, (Time.deltaTime * (rotspeed * 2)));
 }

 if(Input.GetAxis("Mouse Y") < 0 && target.transform.position.z > 773){
     firingForm = Vector3.Distance(placeHolder.transform.position, target.transform.position);
     target.transform.Translate(0, 0, (Time.deltaTime *(rotspeed * 2) * -1));
 }
 
 if(Input.GetKey("space")){
     Launcher.transform.rotation = originalRotation;
     target.transform.position = originalPos;
     throwThis = originalThrow;
 }
 
 if(Input.GetButtonDown("Fire1")){
     firebomb();
 }

}

function firebomb() {

 animation.CrossFade("fire");
 yield WaitForSeconds(1);
 throwThis = originalThrow - ((originalDist - Vector3.Distance(placeHolder.transform.position, target.transform.position)) *35);
 var clone = Instantiate(grenade, placeHolder.transform.position, placeHolder.transform.rotation);
 clone.rigidbody.AddRelativeForce(Vector3.forward * (throwThis));

} Thank you for your help.