After too many attempts to login
If you have an iPad and don’t want anyone else to access your device while you are away or not using it, then you can set a security passcode that has to be entered in order to gain access to the Home screen.
Whenever you turn on, restart, sleep or lock the screen on your iPad, you’ll be asked for the passcode. It’s pretty useful if you have sensitive information or use apps like Mint and don’t want people snooping around. However, if you forget the passcode or if you have kids who get a hold of your iPad while you’re not watching, then you can run into the this dreaded message.
If you enter the wrong passcode on your iPad, you’ll get a message like the following:
If you keep entering a wrong password, your iPad will become disabled for a certain period or time, such as 1 minute.
Finally, if you continue entering a wrong password, the iPad will become disabled for longer periods of time. Eventually, it’ll say you must connect it to iTunes on the last computer it was synced with in order to regain access to your iPad.
If you’re getting this message, it means there were numerous attempts to access your iPad that failed. Simply connect it to the computer you last synced it with and initialize a sync. Once you do that, you can enter the correct passcode and you’ll be into your device.
If you forgot your iPad password altogether, you have to perform a restore on the computer that you last synced it with. If you try to restore on a different computer that you never synced your iPad with, you will be able to remove the passcode and unlock the device, but none of your data will be there, so be careful!
If you’re a MobileMe user, you can remotely change or reset your iPad password by using the Find My iPhone feature.