Updated so the wallet can check your balance before trying to send coins.
Secure TNB Wallet Extension.
Putting Wallet keys directly into websites is not safe or secure.
On some blockchains, you never have to enter your wallet keys into a website at all, you can just use a browser extension, which websites can interface with to securely store your keys and broadcast transactions to the blockchain.
Keysign aims to bring security and ease-of-use to thenewboston chain.