my Internet Explorer works properly on some sites and on others it does not work,I would like to know what does it mean when the Internet Explorer displays certificate errors and how can I recover from them?
It depends upon the error. Some certificate errors stem from the site using a self-signed certificate (That is on that was not signed by a Certificate Authority). Some errors stem from a certificate for one domain (or sub domain) being used on another domain (such as a certificate signed for 'server.example.com' being used on 'otherserver.example.com').
Depending upon the type of error, there may be little you can do.