Failure to assign a prefab to a variable

When i run this script and the objects collide unity tells me i have failed to assign my prefab correctly(giving me the error “The Variable Cubeprefab of ‘Cubeinteractions’ has not been assigned” the moment there is a Collision). Any one care to help the scripting illiterate?

using UnityEngine;
using System.Collections;


public class Cubeinteractions : MonoBehaviour {
	
	public Rigidbody Cubeprefab;
	
void OnCollisionEnter(Collision collisioninfo){
	
		float boxmass = collisioninfo.rigidbody.mass;
		
		
		if(boxmass == rigidbody.mass){
			GameObject boxgameobject = collisioninfo.gameObject;
			Rigidbody Cube1 = Instantiate(Cubeprefab, transform.position, transform.rotation) as Rigidbody;
			Destroy(boxgameobject);
			Destroy (gameObject);
			}
			
	}
}

I assume the problem is here “public Rigidbody Cubeprefab;”

What ZenithCode said is right, in the Inspector panel in the Unity editor window when you click on the object that you’ve assigned the code to it should show the name of your code, below that there should be a slot that says “None (Game Object)”. Drag and drop the prefab there and it should work. When you get this error the debugger is basically telling you that you didn’t put anything in the slot or didn’t have anything being automatically put in there (by code).