When a user visits a secure (HTTPS) page that has been blocked, the alert for block pages is not displayed.
If a user goes to a HTTP website, it will show the alert for blocked pages correctly.
If a user goes to a HTTPS website, it will show "This page can't be displayed", or a white page.
Displaying the Block Alert page for secure pages requires Web Security.cloud to be able to intercept the secure connection by Activating HTTPS Inspection.
In order to enable HTTPS Inspection, you must first install the Symantec Root CA for the client machines.
Once you have enabled HTTPS Inspection, Web Security.cloud will be able to intercept the encrypted connection and insert the Block Alert Page for blocked websites.