Firefox userChrome.css

/*
 * Do not remove the @namespace line -- it's required for correct functioning
 */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
@namespace html url("http://www.w3.org/1999/xhtml");
@namespace svg url("http://www.w3.org/2000/svg");
/* set default namespace to XUL */

/* Hide TreeStyleTab header */
#sidebar-header {
  display: none;
}

/* Hide top tab bar */
#TabsToolbar {
   visibility: hidden !important;
}

/* Change url bar color */
#TabsToolbar, #tabbrowser-tabs, #nav-bar, #toolbar-menubar, #browser-panel {
   background-color: rgb(50, 50, 52) !important;
}

/*  Move the window buttons down and the menu icon to the left */
#nav-bar {
   border-width:1px !important;
   border-style: solid;
   border-color:transparent !important;
}
#nav-bar {
   margin-bottom: -1px !important;
   margin-top: -29px !important;
   margin-right: 140px !important;
   margin-left: 0px !important;
}