There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

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

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

What do the security warning codes mean

thank you Fred!

alas, the info you sent me is a litle bit over my head.. so could you just answer this one question from my previous post simply?

"would attackers be able to steal such information if i never enter any? ie, if i only visit the site to read about things..."

much appreciated!!!

A secure connection prevents anyone in the electronic chain between your browser and the web server from seeing what is sent back and forth. My biggest concern would be sending login credentials or personal/financial information over an open connection, since if those were stolen, the consequences could be very serious. But for people in some places, just having someone watch and record what you are reading/viewing could be a big problem.

But most sites these days do support a secure connection, so if you see this error page often, there may in fact be a "man in the middle" of your connection. That could be your security software, or it could be nosy tracking software, or... anyway, we suggest trying to track it down.

When you get the error page and click the Advanced button, what error code is shown? For example, SEC_ERROR_UNKNOWN_ISSUER.

This article describes the common reasons behind different error codes if you want to read ahead: How to troubleshoot security error codes on secure websites.

awesome, thank you so much!