Player move script

I am new to unity. I wrote a very short script to enable the player to move forward. Here is the error:

The script:

using UnityEngine;
using System.Collections;

public class 0 Gravity : MonoBehaviour {

	// Use this for initialization
	void Start () {
		public float speed 10;
		public float rigidbody rb;
	}
	
	// Update is called once per frame
	void Update () {
	if (Input.GetKey ("up"))
		{
			rb.AddForce(transform.speed "up")
		}
	}
}

Your line 4 has a zero character. Delete that and your script should compile.