Hi
I have some 3d models and i want to import them to unity3d but when i import them some faces of model is damaged or some parts are moved to other places or even some parts deleted hidden 
please help me!!
I hope you are importing .FBX model in your project. when you are creating a model you should need to packed all parts of model in single object. It will be very helpful for you then there position is not changed no problem of missing any part.
Thanks a lot!!
but what can i do with hidden faces?