.tabbrowser-tab[unread], background-image: linear-gradient not working in userChrome.css

Question

I had this working before but now it stopped working. I have some code in my userChrome.css to create a small grey triangle in the top right corner of an unread tab.

/* Mark new and unread tabs */
.tabbrowser-tab[unread] {
  font-style: italic; 
  background-image: linear-gradient(-135deg, rgba(100, 100, 100, 0.6) 10px, transparent 0);
}
.tabbrowser-tab[busy] {
  font-style: italic;
}
.tabbrowser-tab[pending] {
  font-style: italic;
}
.tabbrowser-tab:not([pinned]) {
  min-width: 10px !important;
}

/* Move Find Bar above the page */
.browserContainer > findbar {
  -moz-box-ordinal-group: 0;
}

It is the first part .tabbrowser-tab[unread] that is not working. Is there something wrong in my csscode?

I'm running Firefox 61.0.1 64-bit on Ubuntu.

Answer 1

The unread tag has been removed see https://bugzilla.mozilla.org/show_bug.cgi?format=default&id=1453957