iCloud: If you can’t sign in to iCloud.com
If you have trouble signing in to iCloud.com, try the following:
When typing your password, make sure the Caps Lock key isn’t on (passwords are case-sensitive).
Make sure you’re typing the Apple ID email address and password that you used to create your iCloud account. For example, youriCloudaccountname@gmail.com or youriCloudaccountemail@iCloud.com.
03/24/14 Exclude the following item until two-step verification is available
If you set up your iCloud account to require two-step verification, make sure you correctly enter the latest code sent to your device.
If you can’t remember your password, or you see a message that your account has been disabled for security reasons (which might happen if someone tried and failed to sign in multiple times), you need to change or reset your password.