You will get a Security Alert window when the certificate in Windows Internet Explorer expires. This certificate identifies you as an authentic user when visiting secure Web sites (i.e. banks), and it also verifies the authenticity of these sites without you checking their credentials.

If you get this window when visiting a Web site you trust, you can click Yes and proceed. If you wish, you can select View Certificate to verify the Web site's credentials. To avoid seeing this window in the future, you should update your browser's root certificate. Follow these steps to do so:

1. Click on Tools and select Internet Options.
2. Click on the Content tab.
3. Click on the Certificates button.
4. Click on the Trusted Root Certification Authorities tab.
5. Click at the top of the Expiration Date column to sort by date.