White outline on the sides of tabs and across the top of the address bar.

[TheReverend403]

Environment:
Firefox Version: 89.0
OS: Windows
Theme: Dark

[black7375]

It has been confirmed to appear in some themes.

/* photon */
#navigator-toolbox:-moz-lwtheme {
    --tabs-border-color: rgba(0,0,0,.3);
}

/* proton */
:root {
  --tabs-border-color: threedshadow;
}

---

The line that appear around the tabs are intentional.

[TheReverend403]

They don't look intentional when compared to the exact same CSS on Linux. They're far more subtle compared to Windows where it's just a solid white line.

[TheReverend403]

For the record, I've made some slight customisations to the photon-style branch, nothing that should affect borders between tabs though.

_userChrome.css is userChrome.css from this repo.

@import url("_userChrome.css") screen;

:root {
    --autocomplete-popup-highlight-background: #8c54fe !important;
    --focus-outline-color: #8c54fe !important;
    --lwt-popup-brighttext-url-color: #b5b5b5 !important;
    --url-match-color: #fd971f;
}

#urlbar:is([focused]) > #urlbar-background, #urlbar-container .urlbar-input-box {
    border-color: var(--focus-outline-color) !important;
}

.urlbarView-row:not([selected]) .urlbarView-title strong,
.urlbarView-row:not([selected]) .urlbarView-url strong {
    color: var(--url-match-color) !important;
}

[black7375]

Oh, I checked. I will check it.
I think I forgot to delete it by mistake.

---

I adjusted a few more things.
Now it looks much better than before.

This commit will be merged while working on an upcoming release.
32bafa7

[black7375]

The surest way is to remove box-shadow.

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

But some themes need box-shadow, so it will provided by wiki.
https://github.com/black7375/Firefox-UI-Fix/wiki/Compatibility-Issues-Solution#white-outline-on-the-top-of-address-bar