My interface customizations for Firefox to live without Classic Theme Restorer

userChrome.css

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

.tabbrowser-tab:not([pinned]):not([selected]) {
    min-width: initial !important;
    overflow: hidden;
}

.tabbrowser-tab:not([pinned]) {
    min-width: initial !important;
}

.tabbrowser-tab {
    border-right: 1px solid #aaa !important;
}

/* dividers between tabs */
.tabbrowser-tab::after,
.tabbrowser-tab::before {
  display: none !important;
}