This connection is untrusted
Some times you can face the Warning message "This connection is untrusted" when accessing secured (SSL certified - https://) websites such as Mail site, Banking site. But this is not an issue.
The main reason of the Warning message is Date and Time were changed in your Computer caused by CMOS (BIOS) battery fail in Mother board. After replaced battery, modify the Date and Time. Now your problem will be resolve.