Hi, is this problem on a Mac (Mac OS) or on an iPhone/iPad iOS)?

This issue is on a desktop iMac. Have worked out the printer issue, but still have the potential security alerts. Thank you.

Thanks, Jim. An expired certificate is a possibility with a device that doesn't get any updates. Website certificates also expire, although usually that is remedied within a few days. If you see lots and lots of these messages, your system clock might be set to a future date.

For other kinds of connection error pages, could you copy/paste from the error page into a new reply with the explanation and/or error code. Sometimes you need to click an Advanced button to get the full story.

Firefox also has a phishing and malware protection feature which can show a red page. (How does built-in Phishing and Malware Protection work?) Since you didn't mention a red page, it's probably not that.

If you get some other kind of security alert besides the ones I mentioned, it's possible those are a scam to sell you security software or services. Sometimes they are delivered through ad networks and sometimes by an add-on. It's worth checking your add-ons for anything that doesn't belong. Here's how:

Open the Add-ons page. Either:

• Command+Shift+a (Windows: Ctrl+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions. On the right side, find the "Manage Your Extensions" heading.

If there is at least one extension before the next heading -- "Recommended Extensions" -- please continue:

Then cast a critical eye over the list below that heading. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything that mentions search, or privacy, or looks suspicious, or that you just do not remember installing or why? If in doubt, disable (or remove). For your privacy and security, don't let mystery programs linger here.

Any improvement?

If your Add-ons page is blank or is blocked, you can restart Firefox in its Troubleshoot Mode to do the above review:

In its Troubleshoot Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to bypass issues that can cause problems with pages.

If Firefox is running:

You can restart Firefox in Troubleshoot Mode using either:

• "3-bar" menu button > Help > Troubleshoot Mode... (before Fx88: Restart with Add-ons Disabled)
• (menu bar) Help menu > Troubleshoot Mode... (before Fx88: Restart with Add-ons Disabled)

and OK the restart. A small dialog should appear. Click the Open button (before Fx88: "Start in Safe Mode" button).

If Firefox is not running:

Hold down the option/alt key when starting Firefox. (On Windows, hold down the Shift key instead of the option/alt key.) A small dialog should appear. Click the Open button (before Fx88: "Start in Safe Mode" button).

Note: Don't use the Refresh without first reviewing this article to understand what will be deleted: Refresh Firefox - reset add-ons and settings.

If it's all clean, that's great news and we can rule that out as the potential source of the problem.