Help please! I sent all my ether to a fraud website about an hour ago. I tried contacting the email that was on website, but it said it was invalid.I need to cancel it ASAP.
No. Ethereum transactions are final and cannot be undone. Assuming an actual transaction was made and was already mined into a block, nothing can now undo it, so you're at the mercy of whoever controls the account the ether was sent to.
Just to confirm, do you have a transaction hash and you see that transaction on etherscan.io as having completed successfully? If so, then I'm afraid there's nothing you can do.