userChrome.css

@-moz-document url("chrome://browser/content/browser.xul") {
    .tabbrowser-tab {
        -moz-box-flex: 0 !important;
        min-width: -moz-min-content !important;
    }
    .tabbrowser-tab[pending] {
        opacity: 0.5 !important;
    }
    .tab-close-button, .tab-label-container, .tab-loading-burst {
        display: none !important;
    }
    .tab-icon-image, .tab-throbber, .tab-throbber-fallback {
        margin: 0 !important;
    }
    .tab-icon-image:not([src]) {
        display: -moz-box !important;
    }
    .tabbrowser-tab[busy] .tab-icon-image {
        display: none !important;
    }
    .panel-viewcontainer[panelopen], .panel-viewstack, statuspanel {
        transition: none !important;
    }
    #search-container {
        min-width: 32ch !important;
    }
    /* oldscool layout */
    #PersonalToolbar {
        -moz-box-ordinal-group: 8999 !important;
    }
    #TabsToolbar {
        -moz-box-ordinal-group: 9000 !important;
        background-color: var(--chrome-secondary-background-color) !important;
        background-image: none !important;
        color: var(--chrome-color) !important;
    }
    #navigator-toolbox:after {
        -moz-box-ordinal-group: 9001 !important;
    }
    #TabsToolbar:after {
        display: none !important;
    }
    #TabsToolbar:not([collapsed="true"]) + #nav-bar {
        box-shadow: none !important;
        border: 0 none !important;
    }
    #navigator-toolbox > toolbar:not(#toolbar-menubar):not(#TabsToolbar):not(#nav-bar) {
        transition: none !important;
        padding: 1px 6px 5px !important;
    }
    #navigator-toolbox .chromeclass-toolbar-additional {
        max-width: none !important;
    }
    /* .tab-throbber-fallback uses apng instead of css animation */
    .tab-throbber {
        display: none !important;
    }
    .tab-throbber-fallback[busy], .tab-throbber-fallback[progress] {
        display: unset !important;
    }
}