How to control position of GUITexture when its inside a prefab

Hi Everyone,

Sorry for my bad English because of I am not a native speaker of English, but I am trying to writing very simple so you can understand me.

I am new with Unity and facing problem with positioning a GUITexture inside a Prefab. That is it's positioned correctly as I set in transform component and always disappear from the Prefab.

I've read in http://docs.unity3d.com/Manual/class-GuiTexture.html, it says that " and they are measured in Screen Coordinates, rather than World Coordinates.". So how can I control GUITexture's when it is inside a Prefab?

Many thanks!