Help with C# coding a loaded button (3.x Game Development Essentials)

Hey everyone! I've been following Will's excellent new book "3.x Game Development Essentials" and fished it earlier today, however there is a small hiccup causing me some annoyances... In the book he creates a Play button, but if the game is to be loaded in a web player, this play button is replaced by a "loading" button, until 100% has been loaded, and then the button should swap back over to play. My problem lies with 2 things; 1. This button also appears on the Standalone version 1. The button is always there. Above my play button, the "Loading..100% loaded" is always visible (this doesnt prevent you from clicking the play button though) I checked over the book plenty of times, but simply cannot figure out where I went wrong, I'm pasting my entire "MenuButtons" script below, hoping for some help (:

using UnityEngine; using System.Collections; [RequireComponent (typeof (AudioSource))]

public class MainMenuGUI : MonoBehaviour {

public AudioClip beep; public GUISkin menuSkin; public Rect menuArea; public Rect playButton; public Rect instructionsButton; public Rect quitButton; Rect menuAreaNormalized; string menuPage = "main"; public Rect instructions;

 void Start() {
 menuAreaNormalized = new Rect(menuArea.x * Screen.width - (menuArea.width * 0.5f), menuArea.y * Screen.height - (menuArea.height * 0.5f), menuArea.width, menuArea.height);
     
     }
 
 void OnGUI() {
     
     GUI.skin = menuSkin;
     GUI.BeginGroup (menuAreaNormalized);
     
     
 if(menuPage == "main") {
             
         if(Application.CanStreamedLevelBeLoaded("Island")){
             if(GUI.Button(new Rect (playButton), "Play")) {
                 
                 StartCoroutine("ButtonAction", "Island");
             }else{
             
                 float percentLoaded = 
                 Application.GetStreamProgressForLevel(1) * 100;
             GUI.Box (new Rect(playButton), "Loading.." + percentLoaded.ToString("f0") + "% Loaded");
         }
     }
         
             if(GUI.Button(new Rect (instructionsButton), "Instructions")) {
                 audio.PlayOneShot(beep);
                 menuPage="instructions";    
         }
         
         if(Application.platform != RuntimePlatform.OSXWebPlayer && Application.platform != RuntimePlatform.WindowsWebPlayer){
         if(GUI.Button(new Rect (quitButton), "Quit")) {
                 StartCoroutine("ButtonAction", "quit");    
             }
             
         }
     } else if(menuPage == "instructions") {
         GUI.Label (new Rect(instructions), "You awake on a mysterious island... Find a way to signal for help or face certain doom!");
         if(GUI.Button (new Rect(quitButton), "Back")) {
             audio.PlayOneShot(beep);
             menuPage="main";
         }
     }
     
 
 GUI.EndGroup();
 }
 

 
 IEnumerator ButtonAction(string levelName) {
     audio.PlayOneShot (beep);
     yield return new WaitForSeconds(0.35f);
     
     if(levelName != "quit") {
         Application.LoadLevel (levelName);
     }else{
         Application.Quit ();
         Debug.Log ("HaveQuit");
     }
 }
 
 }

The specific snippet affecting the button is here;

if(Application.CanStreamedLevelBeLoaded("Island")){ if(GUI.Button(new Rect (playButton), "Play")) {

             StartCoroutine("ButtonAction", "Island");
         }else{

             float percentLoaded = 
             Application.GetStreamProgressForLevel(1) * 100;
         GUI.Box (new Rect(playButton), "Loading.." + percentLoaded.ToString("f0") + "% Loaded");
     }
 }

Thank you so much in advance!