When you visit certain web sites in Firefox, you might get an error message that says something similar to the following:

site address is a site that uses a security certificate to encrypt data during transmission, but its certificate will not be valid until date/time.

To try to solve this problem, just double-click on the time in the lower right corner on the Taskbar and set the time correctly. Be sure to check the time, month, date and the year. As soon as it is corrected, this will usually fix this issue.