Why my tracking No. is invalid?

Why my tracking No. is invalid?
Sometimes the tracking No. given you is invalid, and you think we cheat you, dont be worried. Please read the following three possibilities:

• Our courier hasn’t updated the recent delivery information to their website.
   
• The tracking code was not correct, maybe one letter of the tracking No. is incorrect.
   
• The parcel has been delivered a long time ago. Some shipping companies will remove the tracking code history.