Loading a Scene through a GUI button

I have a scene where I have made a GUI scrolling menu. My setup is like this : First you have a button called “Start”. On pressing that I get a panel with 3 more GUI buttons. One of them is to load a scene. When I run the script in the editor, as soon as I press start the scene pops up whereas the menu does not appear. How do I achieve this? As soon as I press the start button I should go to the next menu,then choose the level load button to load the scene. I am not able to understand why the scene loads immediately

This is the code:
private Animator anim;
public GameObject menupanel;
private bool start = false;
private bool load = false;

	void Start () 
	{
		anim=menupanel.GetComponent<Animator>();
		anim.enabled = false;
	}
	// Update is called once per frame
	public void Update () 
	{
	      if(Input.GetMouseButton(0)&&!start)	
	       {

			ShowMenu();

	       }
		else if(Input.GetMouseButton(0)&&!load)
		{
			SceneLoad();
		}

	}
	public void ShowMenu()
	{
		anim.enabled = true;
		anim.Play("New Animation");
		load=false;
		start = true;
	
	}
	public void SceneLoad()
	{
		start = false;
		load= true;
		Application.loadlevel("Scene1");
	}
}

It’s auto loading because the GetMouseButton will be active in 2 frames, so both cases are triggering one after the other.

Frame 1 calls ShowMenu then sets load=false;
Frame 2 !load is now valid so your level loads.

You’ll be better off using GetMouseButtonDown, or use proper Unity 4.6 buttons.