Simple OnGui does not work

I tried everything to get this working but somehow I can't...

using UnityEngine; using System.Collections;

public class GameManager : MonoBehaviour {

 public static int playerScore01 = 0;  
 public static int playerScore02 = 0;
 



 

 public static void Score (string wallName) {   
     if(wallName == "_rightWall")
     {
         playerScore01 += 1;
     }

     else 
     {
         playerScore02 += 1;
     }
     Debug.Log ("Player Score 01 is" + playerScore01);
     Debug.Log ("Player Score 02 is" + playerScore02);



 
 }


 void OnGui() {

     GUI.Label (new Rect (Screen.width / 2 - 150, 20, 100, 100), "bla");
     GUI.Label (new Rect (Screen.width / 2 + 150, 20, 100, 100), "bla");


  }

 }

I think the code is fine, but somehow I can't see the GUI when testing the game... is there a problem in the code I am to dumb to see?

Please help...