When running a test purchase through the checkout page with Authorize.net an error message is returned saying
Phone number is required or
Bill To Zip/Postal Code is required or
Card Code is required.
Authorize.net is returning this error because the form settings are configured in Authorize.net to ensure that these values are passed when a new order is placed. To keep this error from showing up you just need to modify the form settings in Authorize.net to make these values optional. Read this article to learn how to configure the Authorize.net form settings.