#TabsToolbar { display: none !important; }
#sidebar-box #sidebar-header { display: none !important; }

* { border-radius: 0px !important; }

#tabbrowser-tabs {
  counter-reset: tab-counter;
}

.tabbrowser-tab {
  counter-increment: tab-counter;
  position: relative;
}

.tabbrowser-tab::after {
  content: counter(tab-counter);
  position: absolute;
  bottom: 2px;
  right: 2px;
  font-size: 10px;
  color: white;
  background: rgba(0,0,0,0.6);
  padding: 1px 4px;
  border-radius: 3px;
  pointer-events: none;
}