grav-admin-first/user/plugins/admin/themes/grav/templates/partials/noscript.html.twig

<style>
.error-message {
  background-color: #fce4e4;
  border: 1px solid #fcc2c3;
  width: 100%;
  padding: 20px 30px;
}
.error-text {
  color: #cc0033;
  font-family: Helvetica, Arial, sans-serif;
  width: 100%;
  font-weight: bold;
  line-height: 20px;
  text-shadow: 1px 1px rgba(250,250,250,.3);
}
.full-height {
  display: block;
  width: 100%;
  height: 100%;
}
</style>

<div id="noscript" class="full-height">
    <main id="admin-main" class="full-height">
        <div id="titlebar" class="titlebar">
            <h1><i class="fa fa-fw fa-exclamation-triangle"></i>{{ "PLUGIN_ADMIN.ERROR"|tu }}</h1>
        </div>
        <div class="full-height">
                <div class="error-message {% if config.plugins.admin.content_padding %}content-padding{% endif %}">
                    <span class="error-text">{{ "PLUGIN_ADMIN.ADMIN_NOSCRIPT_MSG"|tu }}</span>
                </div>
        </div>
    </main>
</div>

<script type="text/javascript">
  function checkjs() {
    var element = document.getElementById("noscript");
    element.style.display = 'none';
  }
  checkjs();
</script>