GUI.Label() does not show up on WebPlayer

I've the following code snippets:

    void OnGUI()
    {
        GUI.Label(new Rect(10, 10, 500, 20), "MyLabel");
    }

It shows up on the Unity3D editor when I hit Play button. It works as expected.

I then Build it to a WebPlayer and run it on the Chrome browser. Everything shows up except the above GUI.Label.

What did I do wrong?

Thanks in advance for your help.