Hmm, is that site-specific? For example, do you have the same problem if you view that screenshot stand-alone in a tab: https://support.cdn.mozilla.net/media/uploads/images/2016-07-19-10-03-08-71ee2f.png

I suspect an add-on might be involved with this problem, but I don't know what is normal for your distribution's version of Firefox. (I'm a Windows user.)

Could you test in Firefox's Safe Mode? In Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

I tried Safe mode and disabled all add-ons . That got rid of the problem. Now to find out Which add-on is causing it. Oh, joy !!! 3:)

Removed this add-on , ... problem solved .

https://addons.mozilla.org/en-US/firefox/addon/image-zoom/?src=search

Glad you found it; probably the name was a strong hint!

I see the issue has been reported on the author's development site, but there doesn't appear to be an official solution yet: https://github.com/jasadams/imagezoom/issues/33

I enjoy the Image zoom add-on but can't use it now due to the problem - after a FireFox update - with the way pages display. I've noticed this is a common occurrence after an update. I've had other extensions fail after FireFox was updated .

When I revisited that github issue, someone linked to a "fixed" version with a funny name:

https://addons.mozilla.org/firefox/addon/image-zoom-ugly-attempt/

But the more general issue remains: most add-ons have built-in assumptions about how Firefox does things and when those assumptions are no longer valid, the add-ons may stop working correctly.