Hide Gameobject

Could someone please tell me how I can hide gameobject?

http://docs.unity3d.com/Documentation/ScriptReference/GameObject-active.html

I tried but I have a problem with unhide gameobject.
Why it does not work?

   void Start()
{
gameObject.active = false;
}

void Update()
{
   if (Input.GetKey ("A"))
		{
			gameObject.active=true;
		}
}

The script only runs if the gameObject it’s attached to is active. Since you set the gameObject to be inactive, the Update function never runs. To get around this, you can just disable/enable the component you are wanting to set inactive.

For instance, if you wanted to disable the renderer on a cube and then show it when you push “A” you could do this.

 void Start()
{
   renderer.enabled = false;
}
 
void Update()
{
   if (Input.GetKey ("A"))
        {
            renderer.enabled = true;
        }
}

Thank you.
Working.