If you are getting a certificate error while visiting a Government website your local trusted certificates may be incorrect.  By running the tool downloaded from this link you will be able to easily install all of the Government certificates that you need to trust those sites.  After running this, if you still get certificate errors, the problem may very well be on the Gov't websites end.


https://iasecontent.disa.mil/pki-pke/InstallRoot_5.2x32_NonAdmin.msi


Simply follow the prompts and read each screen before clicking ahead.