Hi, possible security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connections and send their own certificate. What was the full error message ? *https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can *https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites *https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message *https://support.mozilla.org/en-US/kb/connection-untrusted-error-message *http://kb.mozillazine.org/Error_loading_websites Also before get in to Sync, it is for Syncing (plural) devices and is not meant as a backup service and if use as such will eventually loose your info/data. Please let us know if this solved your issue or if need further assistance.