Which practice can help in maintaining the security of HTML forms on a Web site?

Encrypting credentials submitted via forms is a key practice for maintaining the security of HTML forms on a website. When users submit forms that contain sensitive information, such as passwords or personal data, it's crucial to protect that information during transmission from the user's browser to the server.

Encryption converts the credentials into a format that is not easily readable to anyone who might intercept the data as it travels across the network. This means that even if an unauthorized party were to capture the data, it would be unreadable without the appropriate decryption key. This practice helps ensure that user information remains confidential, reducing the risk of data breaches and maintaining user trust.

Other practices mentioned, such as restricting access to certain server files, can enhance overall security but do not specifically address the vulnerability of data in transit that comes with HTML forms. Adding multimedia content to forms does not contribute to security and can even complicate form functionality. Using multiple programming languages for code is more about diverse implementation rather than directly improving the security of HTML forms. Thus, encrypting credentials is the most effective practice in keeping form submissions secure.