Change the appearance of error pages
If you are an Enterprise Threat Protector super administrator, you can configure the appearance of error pages. An error page appears when a user attempts to access a website that violates the Acceptable Use Policy or is a known or suspected malware, phishing, or command and control communication security threat. Error pages appear for known or suspected domains that are configured in the policy with a Block action and the Error Page response. For more information see Error pages.
Any modification that you make to an element or item of an error page is applied to all error pages. For example, if you select a specific font for the message that is provided in an error page, all error pages use that font for the message.