"public GameObject" not appearing in Inspector

First, I'm learning a lot by doing the BurgZergArcade's Hack&Slash RPG Tutorial. Normally, most errors I get are due to some script in which I have made an error, but this one doesn't seems to be an error on my part.

I'm currently jammed at this part or it. http://www.youtube.com/watch?v=Jpi8fRj-wzo&list=SPE5C2870574BF4B06

While I did some modifications (minors ones like adjusting sizes to my liking), I got one thing that isn't working as intended: The Inspector doesn't show any "public GameObject" I input in my C# script when it's linked to an object in the game.

 //This part appear in the Inspector    
 public GUISkin GeneralSkin; 
     
 //This part doesn't appear in the Inspector
 public GameObject playerPrefab; 

I got no compilation error or anything that would normally block the Inspector from updating the script content.

I'm using Unity 4 (Free) and I have read that some functions in the GameObject have been modified/expanded so I'm wondering what I should do to make the any GameObject public so that they appear in the Inspector. (then I could link a prefab to it.)

Thanks for any assistance!