Hi Cathy2019, when the tabs do not all fit, Firefox should show a scroll button at the left end and right end of the Tabs bar, like this:

You don't have that?

Oh, you know what might be faster: If your mouse has a scroll wheel, when the mouse pointer is positioned over the tab bar, scroll up/forward/away to scroll left, and down/toward you to scroll right.

Hi, thanks, yes, I have the arrows to the left and right. but when I click and hold the arrow to the left, the moment I release it it all just heads to the right again, leaving me unable to actually click on any of those tabs. When I use the scroll button as soon as I release the scroll, it all hops to the right again. I was on Firefox developer edition (been using FF at least 20 years), thought it might be an issue with that, so reverted back to plain old FF. Problem remains. I have reinstalled, created new profiles, rebooted, run virus scans, run Spybot.... still the same problem. PLUS: when I click on a drop-down selector, it just flashes and i can't click on my selection, and using the down arrow to select doesn't work either. I changed the mouse, thinking it might be a faulty mouse. Problem still exists. The dropdown issue doesn't happen on another browser. Save my sanity, please.

In the interests of resolving this for anyone else who has the same problem: when I ran FF in safe mode the problem still wasn't resolved. However, when I disabled all my add-ons separately, the browser started behaving itself. Now I need to work out which one is causing the problem.