Android: in which cases Push Notification is rejected upon delivery to devices

Question

I use gcm.jar on the client side and gcm Zend framework on the server side to send push notifications. There are about 100 devices registered for push notifications when they quit, even if I receive a successful message, I don’t click on some of the devices, can I know what the various causes of the failures will be and how to handle them. Any suggestion would be appreciated,

Thanks in advance.