userChrome.css

/* Hide various elements */
#back-button[disabled = "true"],
#forward-button[disabled = "true"],
#new-tab-button,
.scrollbutton-down,
.scrollbutton-up
{ display: none !important; }

/* Hide splitter, when using Tree Style Tab. */
#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] + #sidebar-splitter {
    opacity: 0;
    margin-right: -30px !important;
    width:  30px !important;
    border:  none !important;
}
#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] #sidebar-header {
  display: none;
}
#sidebar { min-width: 10px !important; }