Firefox style: 3ch01c

userChrome.css

@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);
#TabsToolbar { visibility: collapse !important; }

/* Hide the sidebar bookmarks search */
#bookmarksPanel > hbox { display: none !important; }

/* Remove border padding around sidebar */
 .sidebar-placesTree { border: none !important;  padding-top: 10px !important;  background: #111 !important; }

/* Remove Bookmarks title header bar */
/*  #sidebar-header { display: none !important; } */

/* Actual separators */
  .sidebar-placesTreechildren::-moz-tree-separator  { border: none!important;  border-width: 0 !important; }

/* Folders -> Text (Unopened) */
  .sidebar-placesTreechildren::-moz-tree-cell-text(container) { color: #888 !important; font-weight: bold !important; padding-left: 5px !important; }

/* Folders -> Text (Opened) */
.sidebar-placesTreechildren::-moz-tree-cell-text(container, open) { color: #333 !important; }

/* Bookmarks */
.sidebar-placesTreechildren::-moz-tree-cell-text(leaf) { color: #666 !important; padding-left: 3px !important; }

/* Bookmarks (hover) */
.sidebar-placesTreechildren::-moz-tree-cell-text(leaf, hover)  { color: white !important; }

/* Scrollbar */
scrollbar { display: none !important; }

#bookmarksPanel tooltip { color: #333 !important; }

/*Collapse in default state and add transition*/
#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] {
  overflow: hidden;
  min-width: 40px;
  max-width: 40px;
  transition: all 0.2s ease;
  border-right: 1px solid #0c0c0d;
  z-index: 2;
}

/*Expand to 260px on hover*/
#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"]:hover,
#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] #sidebar {
  min-width: 260px !important;
  max-width: 260px !important;
}