Talk to the merchant first. Make sure you have a secure connection to the site. Check the lower left-hand corner of your browser for the symbol of an unbroken lock or key. Don't send credit card information by email - it's not as safe as the secure connection between your browser and the store. Be especially careful if you are accessing the Internet from a cybercafe or other public connection.
Sites show credit card numbers in plain text as typed in.
Someone could watch you type or press the back button as many times as necessary after you log off. The BBC is not responsible for the content of external internet sites.