A site's certificate allows Internet Explorer to establish a secure connection with the site.
If you're operating on an internet explorer web browser, the link below can help you resolve the issue :
https://support.microsoft.com/en-us/help/931850/-there-is-a-problem-with-this-website-s-security-cer...
Another suggestion would be to use a different browser, like Chrome or Firefox to open https://turbotax.intuit.com/
