There is security software like Avast and Kaspersky and BitDefender and ESET that intercept secure connections and send their own certificate.

http://www.ehow.com/how_11385212_troubleshoot-reset-connection-firefox.html

https://support.mozilla.org/en-US/kb/server-not-found-connection-problem

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

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

https://support.mozilla.org/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER

This Connection is Untrusted is sometimes caused because the computer system clock is wrong. Check the time / date / time zone settings.

Hi pineappleseller, when Firefox objects to a site's certificate, it indicates that Firefox could not validate the certificate it was presented when trying to connect. Yahoo knows how to operate a secure server, so most likely the explanation is that the certificate presented isn't the real one. This can be caused by some security software, a proxy server, or malware.

It sounds as though you were able to view the certificate. What info appears for the issuer? I have attached a screenshot for comparison.

If the problem is not that you get a certificate error but that you get this mixed content warning icon --

-- this is just a warning. It's probably because a message has images embedded insecurely. More info in this article: Mixed content blocking in Firefox.

forgot to ask that no one blame security software I do not have loaded or my clock... same suggested fix as last time... do I just wait for firefox to magically accept the existing yahoo mail cert like the last time this happened to a many firefox users? I do not plan to spend 4 hours again chasing stock solutions only to have it resolved ... by firefox on there end.

Thank you for your response. I did get the error message first and firefox slowed to a crawl and could not access mail. I restarted Firefox and the icon you mention is showing up. The Certificate matches 100% to what I pulled and just pulled again. This happened on the inbox page so not sure how to figure what email has unprotected images. The article you linked to seems to say I should not have photos open in yahoo mail. It goes on in the further info link to admit that firefox has some edge sites that are blocked that shouldn't be but they have not been developed or addressed yet. Should I not allow images from yahoo mail in firefox? Thanks for your help on this. I spent 4 hours a few weeks ago on it and never got anything but answers copied from other posts I had read and followed. Still seems it is something that happens randomly vs is catching real issues. I can't remember the last time I received a yahoo message with a photo that opened automatically. I normally get attachments and they work fine.

Hi pineappleseller, I get the mixed content on the Inbox. It seems to be from one of the ad networks, based on a check of the web console. (Screen shot attached.) To use the web console to investigate, you can first open the console using either:

• Ctrl+Shift+k
• menu button > Developer > Web Console

Then type mixed into the search box above the console area toward the upper right, then reload the page. The new console messages will be filtered so you only see ones referring to mixed content (or other messages containing the word mixed, which should be rare).

Each browser probably has a different way of providing information about mixed display content. This is Firefox's current way.

The reason display content is not blocked by default (like some other kinds of mixed content) is that it is considered lower risk. I wouldn't like to see it on a site where I was performing transactions, but for reading/sending email, it's probably okay.

I'm having this problem intermittently. I have two yahoo mail accounts. I open one on Chrome, and it never has a problem. I open the other on Firefox and sometimes it connects and at other times it does not. A few days ago, I downloaded Opera which connected but then Firefox cleared up. Today, neither Firefox nor Opera will connect to yahoo mail. So, I cleared cache and cookies and restarted Firefox. Now, I am able to connect again. It appears that Firefox was either caching something or had a cookie that interfered. I'll see if this works in Opera, too, though I don't use Opera normally so it's likely that it won't.