userChrome.css

/* hide regular tabs */
#TabsToolbar {
  visibility: collapse !important;
}

/* hide TreeStyleTabs sidebar heading */
#sidebar-box #sidebar-header {
  display: none !important;
}

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

/* .treestyletab-tabbar-toolbar { */
/*     opacity: 1.0 !important; */
/* } */

/* .tabbrowser-tabs[treestyletab-mode="vertical"] { */
/*     opacity: 1.0 !important; */
/* } */

/* .tabbrowser-tabs[treestyletab-mode="vertical"] .tabbrowser-tab { */
/*     opacity: 1.0 !important; */
/*     text-shadow: 0px 0px 0px white !important; */
/*     margin-top:    -2px !important; */
/*     margin-bottom: -2px !important; */
/* } */

/* #sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] #sidebar-header { */
/*   display: none; */
/* } */