What happens if the coins are sent to the wrong address? The address I used in error was wrong and when I contacted the site it said that they only used addresses once. Since the address was previously used for a transaction it would no longer be good. I accidentally copied their address when sending bitcoin because it was next to the one I meant to use. The transaction got 505 confirmations. So where does this money go? Can I get it back?
The money is gone. Bitcoin transactions are not reversible by design. Can a bitcoin transaction be reversed?. If you know the owner of the wrong address, you can ask him/her to send you back the money.
Addresses can be used multiple times. If the site has successfully received money on this address before, they have received this payment as well. If they tell you that they didn't receive it, they either throw away private keys (which would be very stupid), don't know what they're doing (which would be a sign to stay away from them), or are trying to defraud you.
In either case you should request that they find your payment for you and either return the money or add it to your balance.