Hi!
Although this site is available over HTTPS (https://w3schools.invisionzone.com) I notice that many site links I follow (e.g. "sign in" and "create new topic") open pages over HTTP.
This is especially problematic for sigh-in form which means that user credentials will be sent to the server over insecure connection. Firefox gives an appropriate warning in such a case.
Please fix this ASAP.
-- rpr.