I just reinstalled windows and this is the message that greets me with a clean install of Firefox when I attempt to go to OutlinerSoftware.com (I should also mention that the site has been unreachable from the federal agency where I work for some time):

Your connection is not secure

The owner of outlinersoftware.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.

Learn more…

Report errors like this to help Mozilla identify and block malicious sites

outlinersoftware.com uses an invalid security certificate.

The certificate is not trusted because the issuer certificate is unknown.
The server might not be sending the appropriate intermediate certificates.
An additional root certificate may need to be imported.

Error code: SEC_ERROR_UNKNOWN_ISSUER

Hmmm... From the outside looking in, the certificate was issued in July 2018 and doesn't expire until July 2019. I can't replicate a problem.

Some companies monitor encrypted web surfing with proxies that terminate and then re-establish ssl connections. It could be the company's man-in-the-middle certificate that's causing the error.

I've noticed this kind of error fairly regularly with Safari in recent weeks. If I type the URL of site that Safari warns about into the location box, instead of clicking the link, then Safari will navigate to the site without warnings -- while using https:// To me, this says there's something broken with Safari and it's not this Outliner Software site, or any other legitimate site's, certificate.

This happens with chrome too, rarely though, it's being over zealous with served certificate dates, just click proceed at own's risk thingy at bottom of that message page. Can check certificates by icon to right of URL address bar iirc. Happens with some other sites too, intermittently.

Icon at Left of URL, not right, iirc.

Seems fine on FireFox, Safari and Chrome for me (macOS 10.14).

--

Andy Brice
https://www.hyperplan.com

I've been seeing a similar warning in Opera on my Android devices.

Following up on my original comment -- I **can** at the moment get to the website on Firefox. It's also reachable via Chrome and Edge.

But Mozilla still gives the site an F: https://observatory.mozilla.org/analyze/www.outlinersoftware.com

Also, lest you think it's just a problem with my computer, this is what happens when I attempt to visit the site via my desktop at work (I work for a federal agency that has stricter security policies than most):

Edge:

Can’t connect securely to this page

This might be because the site uses outdated or unsafe TLS security settings. If this keeps happening, try contacting the website’s owner.

Chrome:

This site can’t be reached outlinersoftware.com unexpectedly closed the connection.

Try:

Checking the connection
Checking the proxy and the firewall
Running Windows Network Diagnostics
ERR_CONNECTION_CLOSED

I was fiddling with a couple of Linux distributions this weekend. I got this same error message, both from Firefox on Live versions of Peppermint OS 9, and the latest Zorin. I'm back on my Windows machine now, running Chrome, and see a "Not Secure" mark left of the URL.

Back in Firefox, clicking through on the advanced tab seemed only to work for a single page, not the whole site.