C# raycast shooting script broken

Here is my script:

 void Update () {
             RaycastHit hit;
             Ray ray  = Camera.main.ScreenPointToRay(Vector3(Screen.width*0.5, Screen.height*0.5, 0));
             
             if (Input.GetMouseButtonDown(0))
             {
                 if (Physics.Raycast (ray, hit, 100))
                 {
                     GameObject particleClone = (GameObject) Instantiate(Effect, hit.point, Quaternion.LookRotation(hit.normal));
                     Destroy(particleClone.gameObject, 2);
                     hit.transform.SendMessage("ApplyDammage", TheDammage, SendMessageOptions.DontRequireReceiver);
                 }
             }
         }

How can I fix it? It is spouting out a bunch of errors. http://gyazo.com/f3b8b52fbdf6661bab373eb0f44d89df