Why appears "Certificate Error" in some blocked websites?

that message appears since you are trying to open a blocked website, using a https secure connection so the browser informs you that the certificate has not been realeased by a reliable/recognized authority it's possible to avoid this error by installing our certification authority on your internal devices here below the guide install the ca to avoid certificate errors docid\ phccnvtkhut1lcf8u74at alternately, in most cases, you can click proceed anyway to force the site to open in this case you will see the filter blocked page