When I sync the apps in iTunes (which I have downloaded before) I recieve such error message:
“…some of the applications in your iTunes library were not install on the iPhone because you are not authorized for them on this computer”
I google it and luckily found the answer in here iPhone Sync: “Some of the applications in your iTunes library were not installed because one or more errors occurred.” – Chris Pratt
In there, some one said to go to the Store menu of iTune, select Authorize computer.
It is the way it is !