If you make a mistake typing an address, your coins are gone.
Are you aware that a bitcoin address has a 4 byte checksum built in to the address?
This means that you have a 1 in 4,294,967,296 chance of making a typo that results in bitcoin address. Assuming you are using a reasonably designed bitcoin wallet to send the transaction, any other typo would be recognized as invalid and the bitcoins wouldn't be sent.