scripts/themes/userChrome.css

@-moz-document url("chrome://browser/content/browser.xhtml")  {
	/* get rid of hamburgers */
	#PanelUI-menu-button {
		display: none;
	}

	/* hide top tabs (for sideberry) */
	#TabsToolbar {
		visibility: collapse !important;
	}

	/* hide sidebar top-menu */
	#sidebar-header {
		visibility: collapse;
	}

	/* change the border between the sidebar and the page */
	#sidebar-splitter {
		visibility: collapse;
	}
}