Could you describe this in more detail? Are those other sites opening in new tabs, or is the current tab changing to one of those sites?

If you haven't already, could you test in Firefox's Safe/Troubleshoot Mode? In that mode, Firefox temporarily deactivates extensions, hardware acceleration, any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem.

You can restart Firefox in Safe/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).

Any improvement?

As a precaution; You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed free to use malware scanners. Each works differently. If one program misses something, another may pick it up.

jscher2000: Other sites were opening in new tabs - ran in Safe mode with no problems but didn't know what I was to do next after seeing the results, in the meantime FredMcd responded - I went to where he suggested, ran Malwarebytes - no results or ideas from that - and ultimately did a reset on Firefox...that seems to have solved the issue (at least so far) - thanks to you both for you quick responses. At least I know where to start looking in the future when things go bad.

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems. Go to that post and click the 'Solved' button to its right.

Don't see anywhere to mark the problem "solved" - no button in sight on my last post.

just found it - think I did it right

Spoke 1 hour too soon - while on Netflix watching a short movie - new tab popped up in the background "style.ca"...so the reset of Firefox didn't work totally...What next?

On all websites causing this problem;

Delete browsing, search and download history on Firefox {web link}

Remove a single website from your history {web link}

Open the History Manager <Control> (Mac=<Command>) <Shift> H. In the search bar, enter the name of the site. Right-click on one of the listings and select Forget About This Site. This should remove all information, including any site settings And Passwords.

Have you added any extensions to Firefox since the Refresh? You can view, disable, and often remove unwanted or unknown extensions on 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 nonessential, 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?