But the hamburger button doesn't usually do that.
Unless you are using weird custom css code.

Frankly, the community was less willing to move to another platform than I had hoped, but perhaps now is a good chance to try again :)

Let's hope so; and thanks for chiming in.

But more importantly - how do you like your new nick: MOG? ;P It sure is easier to type.

[Repost]The FirefoxCSS archive really should be maintained; it is a unique source of info even though many codes are partially outdated.

However, for a long time, the discussions on that sub have been dominated by spammers requesting support for extensions, or showing off useless personal setups.

Then there are the many posters who will not engage in a discussion on css code, simply expecting a quick fix regardless of the complexity of the issue; not to mention the many efforts by contributers which go unanswered.

Since hardly anyone seems to be unduly bothered by the possible demise of that sub - including our very own MrOtherGuy ;) - I assume that there is little if any interest in discussing the finer points of Firefox specific CSS coding.

Thanks very much for the reply; that's pretty much what I experienced; the additional tab corners basically would need to be inside the "physical" boundaries of the tab itself.
Which I found hard to do for some reason, but I'll give it another shot.

I've cobbled together some sort of preliminary "solution" - but the proper term for that thing would probably be hacky. ;)

It might be related to this and/or this issue.

You could try these codes and see if it helps.

#nav-bar:-moz-lwtheme {
   box-shadow: none !important;
}

:root[tabsintitlebar] #titlebar:-moz-window-inactive {
    opacity: 1 !important;
}

If it's the box-shadow causing the issue, in my testing it will only be visible in (most?) 3rd party themes, I couldn't see it in the official Fx and system(Mac) themes either.

On the other hand, that shadow should then go all across the bar, not just show under the selected tab. Unless the chosen theme or his custom css moved things around a bit.

Well, have you tried the code?

It might interfere with the css style, which is creating its own navbar shadow, but that might be (partially?) overriden by current Fx versions anyways. The issue has been discussed in a couple of other forums, seems like the code for that shadow has changed recently.

Again, maybe give this a shot, which has worked for some other users; to be safe put it at the bottom of your userChrome.css, shouldn't matter though:

#nav-bar:-moz-lwtheme {
   box-shadow: none !important;
}

Glad it's working!

As for discussions on it, I've linked to a couple in my first reply, and there's one in a German forum.

Credit for the solution goes to this poster; the related Fx code might be this one.

Thanks mate, great explanation.

I hope it's just a glitch, or the boss mon went too far into his jazz cabbage.

Thanks for the reply, seems like the same issue indeed. Do you happen to know how to target that tooltip, or know it's selector?

Thanks again; I kinda managed to target the highlighters' css with force by js, but it's getting too much trouble at this point.

Well, worth a try.

As for the screenshot, I can't see it; is there one?

You could also take a look at this.

I'm not quite sure what the issue might be, chances are this fedia thing isn't showing me any code or screenshots you might have added to your post.

Just a very wild guess, could it be the nav-bar shadow, which could previously be removed with something like that:

#nav-bar:-moz-lwtheme {
  box-shadow: none !important;
}

Maybe check if there is a that shadow listed in the browser tools, and if so how it is applied in FX123; also if the issue occurs with every theme, or just the ones that are not native Fx or system themes.