Can't get player to move?

I’m currently doing the first tutorial under the “Learn” tab on the website. I am following everything step by step and for some reason, when I press play and try to make the ball move, it won’t move at all. I try w,a,s,d and the up,down,left,and right keys but nothing works. Here is what my script looks like for the rigidbody movement control:
using UnityEngine;
using System.Collections;

public class PlayerController : MonoBehaviour {

private Rigidbody rb;

void start()
	rb = GetComponent<Rigidbody>();

void FixedUpdate ()
	float MoveHorizontal = Input.GetAxis ("Horizontal");
	float MoveVertical = Input.GetAxis ("Vertical");

	Vector3 movement = new Vector3 (MoveHorizontal, 0.0f, MoveVertical);

	rb.AddForce (movement);


So can anybody please help me? I have no clue what I did wrong and i don’t know what to do, I am very new to game programming and have only worked with Microsoft Visual Basic in the past so I do not know a lot about game design as a whole. Thank you in advance for any help.

If I do not have the script attached to the rigidbody, how do I do that? Because I did create the script under the player object, and the rigidbody is attached to the player object. Do I have to do something else to ensure that the script is attached to the rigidbody?