Earlier today we got a question from one of our reader, regarding an error occurred during iOS 4.3.3 restore. “The iPhone could not be restored . This device isn’t eligible for the requested build.”
You may have downloaded the wrong firmware for your device. Make sure you have downloaded a correct firmware for your iDevice.
Click this link (http://gs.apple.com) on the computer you’re using to restore, if you get an Apple 404 page, it’s okay but if you get an index page, just like following screenshot, remove 18.104.22.168 gs.apple.com from your host file and try to restore once again.