userChrome.css

/* Hide Top Tabs */
#TabsToolbar { visibility: collapse !important; }

/* Cleanup treestyle tab css */
#main-window[tabsintitlebar="true"]:not([extradragspace="true"]) #TabsToolbar > .toolbar-items {
  opacity: 0;
  pointer-events: none;
}
#main-window:not([tabsintitlebar="true"]) #TabsToolbar {
    visibility: collapse !important;
}
#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] #sidebar-header {
  display: none;
}
.tab {
  margin-left: 1px;
  margin-right: 1px;
 }

/* Hide Bookmark Button in URL bar */
#pageActionButton,
#star-button-box,
#star-button { display: none !important; }