userChrome.css

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

#PanelUI-menu-button {
    display: none;
}

#TabsToolbar {
    visibility: collapse !important;
}

#back-button, #forward-button {
    display: none;
}

#identity-box, #identity-icon-labels {
    display:none !important
}

#identity-box:hover, #identity-icon-labels {
    display:-moz-box !important
}

@-moz-document url("chrome://browser/content/browser.xul") {
    #urlbar:not([focused]) .urlbar-input-box {
        text-align: center;
    }
}

#urlbar .urlbar-input-box {
    text-align: center;
}

#pageActionButton {
    display: none !important;
}