errors building on android

I have done a "test" game for android. In my computer it's all fine, but in my phone there are some problems... a) The skybox dosn't show up... b) The player vibrates while it's moving or jumping... Here is the movement code:

 #pragma strict
 var speed : float = 6.0;
 var jumpSpeed : float = 8.0;
 var gravity : float = 20.0;
  
 private var moveDirection : Vector3 = Vector3.zero;
 function Update() {
     var controller : CharacterController = GetComponent(CharacterController);
     if (controller.isGrounded) {
         // We are grounded, so recalculate
         // move direction directly from axes
         moveDirection = Vector3(1, 0, 0);
         moveDirection = transform.TransformDirection(moveDirection);
         moveDirection *= speed;
          
         if(Input.touchCount > 0){
             if(Input.GetTouch(0).phase == TouchPhase.Began){
                 moveDirection.y = jumpSpeed; 
            
             }
            
         }
          
         if(Application.isWebPlayer || Application.isEditor || Application.isPlayer){
             if (Input.GetButton ("Jump")) {
                 moveDirection.y = jumpSpeed;
             }
         }
     }else{
         
     }
  
     // Apply gravity
     moveDirection.y -= gravity * Time.deltaTime;
     
      
     // Move the controller
     controller.Move(moveDirection * Time.deltaTime);
 }

I can't overcome all this alone (I tried a lot), so help me please! thank you very much!!!