Is this the only site where you've seen any kind of secure connection / untrusted connection error?

I assume you have visited Greasyfork on this computer before? If so:

When you have a problem with one particular site that previously worked normally, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Clear Firefox's Cache

See: How to clear the Firefox cache

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:

• right-click a blank area of the page and choose View Page Info > Security > "View Cookies"
• (menu bar) Tools > Page Info > Security > "View Cookies"
• click the padlock or globe icon in the address bar > More Information > "View Cookies"

In the dialog that opens, you can remove the site's cookies individually.

Then try reloading the page. Does that help?

It seems I'm having it in a few other sites too. I've been there in another web browser, but not with Firefox. Firefox was freshly installed this morning.

When you get secure connection errors for numerous 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) 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.

1) Time and date are fine. 2) I do have Avast installed, maybe it's doing it? 3) Doesn't seem likely, this computer is only a few days old. And I've had little time to be on it until today.

That test page link loads for me. On the pages that don't load for me, I don't have anything saying I understand or add exception. "Try Again" and "Report This Error" are the only things clickable.

Unfortunately, Firefox does not provide an easy way to inspect a site's certificate with those stripped down error pages. This sometimes works:

(1) In a new tab, type or paste the following internal address into the address bar and press Enter/Return to load it:

chrome://pippki/content/exceptionDialog.xul

(2) In the Location field on that page, type or paste the URL that won't load and press Enter/Return or click Get Certificate

(3) If the View button is enabled, click View to inspect the certificate and take a look at the Issued by section to see whether it points to any locally installed software