Button activating before clicking

Hi. I am following a 2d space shooter tutorial in c#. does anyone know how to fix it so i have to click the button for it to activate? thxxx.

i use notepad++ and have unity 4.2. when i was making the main menu to link to level one, as soon as i click play the button activates.

using UnityEngine; using System.Collections; //go to folders, copy, paste, and change name in notepad and at folder. public class MainMenu : MonoBehaviour {

 #region Feilds
 private string instructionText = "Intsructions:\nPress Left and Right Arrows to move.\nPress Spacebar to fire.";
 private int buttonWidth = 200;
 private int buttonHeight = 50;
 #endregion
 
 
 #region Properties
 
 #endregion
 
 
 #region Functions
 
 void OnGUI () 
 {
     GUI.Label(new Rect(10, 10, 250, 200), instructionText);
     if (GUI.Button(new Rect((Screen.width / 2) - (buttonWidth / 2), 
                         Screen.height / 2 - buttonHeight / 2, buttonWidth, buttonHeight), "Start Game"));
     {
         Application.LoadLevel(1);
     }
     
 }
 
 #endregion

}