Hi mishap, when you get this for pretty much all secure sites, the problem usually is one of the following:

(1) Error in your system's date, time, or time zone, which throws off certificate validity checks. Sometimes allowing computers to use an internet-based time source can introduce this problem.

(2) Firefox not being set up to work with your security software that intercepts and filters secure connections. Products with this feature include Avast, BitDefender, ESET, and Kaspersky; AVG has a Search Shield feature which can cause this error on search sites.

(3) On Windows 10, Firefox not being set up to work with the parental control software Microsoft Family Safety. (To test by turning it off, see: http://windows.microsoft.com/en-us/wi.../turn-off-microsoft-family-settings)

(4) Malware on your system intercepting secure connections.

So... which is it?

If you have any of those specific security products, that would be the first thing to check. We might be able to assist with specific next steps based on what you have if you tell us.

To gather further information, you could inspect a sample certificate to see whether that points to the culprit. If you want to try that now, here's how I suggest starting:

Load my test page at: https://jeffersonscher.com/res/jstest.php

You likely will get an error page. Expand the "I understand the risks" section and look for an Add Exception button.

Note: You don't need to complete the process of adding an exception -- I suggest not adding one until we know this isn't a malware issue -- but you can use the dialog to view the information that makes Firefox suspicious.

Click Add Exception, and the certificate exception dialog should open.

Click the View button. If View is not enabled, try the Get Certificate button first.

This should pop up the Certificate Viewer. Look at the "Issued by" section, and on the Details tab, the Certificate Hierarchy. What do you see there? I have attached a screen shot for comparison.

It does not come back with the COMODO RSA dialogue,its says DIGITALMARKETRESEARCHAPPS PTY and a load of other stuff In the certificate heirachy section it just says jeffersonscher.com

Ive run anti virus and malware scans and un and re-installed firefox and its made no difference

Here is the full message This Connection is Untrusted

You have asked Firefox to connect securely to www.facebook.com, but we can't confirm that your connection is secure.

Normally, when you try to connect securely, sites will present trusted identification to prove that you are going to the right place. However, this site's identity can't be verified. What Should I Do?

If you usually connect to this site without problems, this error could mean that someone is trying to impersonate the site, and you shouldn't continue.

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox only connect to it securely. As a result, it is not possible to add an exception for this certificate.

www.facebook.com uses an invalid security certificate.

The certificate is not trusted because it was signed using a signature algorithm that was disabled because that algorithm is not secure.

(Error code: sec_error_cert_signature_algorithm_disabled)

mishap said

It does not come back with the COMODO RSA dialogue,its says DIGITALMARKETRESEARCHAPPS PTY and a load of other stuff

That sounds like some kind of spyware. Why is it "researching" all your secure communcations? In a thread from 2012, it was linked to something called the E-Rewards Notify App. Do you have anything like that?

Here's my suggested procedure for tracking down and cleaning up bad add-ons, hijackers, and ad injectors. I know it seems long, but it's not that bad.

(1) Open the Windows Control Panel, Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. Be suspicious of everything you do not recognize/remember, as malware often uses important or innocent sounding names to discourage you from removing it. Take out as much trash as possible here.

(2) Open Firefox's Add-ons page using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons
• in the Windows "Run" dialog, type or paste
  firefox.exe "about:addons"

In the left column, click Plugins. Set nonessential and unrecognized plugins to "Never Activate".

In the left column, click Extensions. Then, if in doubt, disable (or Remove, if possible) unrecognized and unwanted extensions. Bear in mind that all extensions are optional, none come with Firefox, and you can learn more about them by checking their reviews on the Add-ons site.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Any improvement?

(3) You might already have covered this, but just in case, you can search for remaining issues with the scanning/cleaning tools listed in our support article: Troubleshoot Firefox issues caused by malware. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case.

Success?

I had a programme called E Rewards notify app. In control panel this was listed as published by Digital Market research. This has been uninstalled and I have complained about malware. As I uninstalled it,AVG came up with an infection warning,so I let it clear it up.I also disabled or removed several Firefox add-ons and plug-ins, Also I found that in the LAN setting in Internet Options box,it had been set to use a proxy server for for your LAN.When i changed this to automatically detect settings...the problem connecting to secure sites disappeared immediately. Hope you can make sense of this rambling. Hopefully this will now have cured my problem.Thanks again for your help