Problem with the "Play again" button.

Ok so here’s something that I really don’t get. Here’s the code:

#pragma strict

function OnGUI () {
GUILayout.Button("Play again!"); // It should make a button in the corner saying "play again" :(
}

Yet when I run the game the button doesn’t appear. Mods if you reject this question please answer the other sub-questions I have to do with this topic.
Thanks!

This is using the old GUI style:

    if (GUI.Button (Rect (20,40,80,20), "Level 1")) {
        Application.LoadLevel (1);
    }

You can use the new UI system to create a canvas and add a button. Then write a script to determine what happens when you press the button.