UnityException: Tag: Ball is not defined. CameraTracksPlayer.Start () (at Assets/CameraTracksPlayer.cs:12)

Questions & Answers
1

using UnityEngine;
using System.Collections;

public class CameraTracksPlayer : MonoBehaviour {

Transform player;

float offsetX;

// Use this for initialization
void Start () {
	GameObject player_go = GameObject.FindGameObjectWithTag("Ball");**ERROR**

	if (player_go == null) {
		Debug.LogError("Couldn`t find an object with tag 'Ball' ! ");![65687-22.png|1900x1009](upload://6SZ65ZHaxs2uvyIU6ZJZHy3gMyi.png)
		return;
	}

	player = player_go.transform;

	offsetX = transform.position.x - player.position.x;//x

}

// Update is called once per frame
void Update () {
	if (player !=null){
		Vector3 pos = transform.position;
		pos.x = player.position.x + offsetX;
		transform.position = pos;
	}

}

}

2

Maybe something more like this

 Player = GameObject.FindWithTag ("Ball");