Since the HTML protocol adaptor relies on HTTP messaging, it also implements password protection. The agent application specifies the list of allowed login identifiers and their password when creating the HTML adaptor. When password protection in enabled in HTML, the web browser usually displays a dialog box for users to enter their login and password.
In general, the security mechanisms of a protocol adapter depend upon the security features of the underlying protocol. The ability to use security mechanism also depends upon the functionality of the management console. If your web browser does not support the password dialog, you will not be able to access a password-protected HTML adaptor.