Thin Tabs (the addon from addons.mozilla.org)

/*
     * This Source Code Form is subject to the terms of the Mozilla Public
     * License, v. 2.0. If a copy of the MPL was not distributed with this
     * file, You can obtain one at http://mozilla.org/MPL/2.0/.
     *
     * This is a fork of Small Tabs, written by ロシア,
     * https://addons.mozilla.org/en-US/firefox/addon/small-tabs/
     */

    @namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

    @-moz-document url(chrome://browser/content/browser.xul) {


    #TabsToolbar {
    }

    .tab-background-start::after,
    .tab-background-start::before,
    .tab-background-start,
    .tab-background-end,
    .tab-background-end::after,
    .tab-background-end::before,
    .tabbrowser-tabs {
        /* Force that these items do not have a minimum height. This is
         * especially needed for supporting TabMix Plus. */
        min-height: 0px !important;

        /* Make sure that the text is correctly aligned. */
        -moz-box-align: none !important;
    }
    /* Needed to make sure that the tab bar will not grow by one pixel
     * if it overflows. */
    #TabsToolbar > #alltabs-button,
    #TabsToolbar > #new-tab-button,
    #tabbrowser-tabs > .tabbrowser-arrowscrollbox > * {
        margin-bottom: 0px !important;
    }

    /* This is the box at the left and right of the tabs. */
    #tabbrowser-tabs > .tabbrowser-arrowscrollbox > .arrowscrollbox-scrollbox {
        -moz-padding-end: 0px !important;
        -moz-padding-start: 0px !important;
    }
    /* The image of the tabs. */
    .tab-throbber,
    .tab-icon-image {
    }

    /* The image of not pinned (normal) tabs. */
    .tab-throbber:not([pinned]),
    .tab-icon-image:not([pinned]) {
        /* Consume some of the space to our left to move the text closer if there is an icon. */
        -moz-margin-end: -2px !important;
    }
    /* The image of not pinned (normal) tabs. */
    .tab-throbber:not([pinned]),
    .tab-icon-image:not([pinned]) {
        /* Consume some of the space to our left to move the text closer if there is an icon. */
        -moz-margin-end: -2px !important;
    }

    /* The contents of the tabs. */
    .tab-content:not([pinned]) {
    }

    /* The label which holds the site name. */
    .tab-text.tab-label:not([pinned]) {
        /* Move the text away from the left edge, especially needed if there is no icon. */
        /* Part of this is consumed again by the image. */
        -moz-margin-start: 5px !important;
    }

    /* The close button of the tab. */
    .tab-close-button:not([pinned]) {
        -moz-margin-start: 0px !important;
    }


}