1. Check your computer's date and time. If they are incorrect, you will receive security certificate errors. Click on the time in your taskbar, and set the correct time in the pop-up window. Refresh the website where you received the error message. If you receive a security certificate error message again, the problem lies with the website's security certificate.
2. Click the icon that looks like a padlock next to your browser's address bar.

3. Read the information in the window. This will detail who owns the website, the site's verification status and any known information about the website's trustworthiness. Compare this to what you know about the site you were attempting to visit.
4. Click 'View Certificates, then 'Install Certificates.'
5. Click 'Yes' at the security warning to install the certificate for the website.