Yes, I know it. It is a disadvantage of this approach. We use JavaScript to disable error-block if JavaScript is enabled in the browser. In this case we need some time to process it. Usually it is really fast, but sometimes user can see popup/error message during page is loading.

We've moved JavaScript immediately after the erro message ( commit 62d7504 ). It might decrease this delay of popup showing for you.

If you have any other propositions, please share them with me ) In any way, I really appreciate your comments!

the no js notification often displays for a brief moment

I've added this css code in order to give browser a time for page rendering. It should help. You can customize it in case you want to have some cute css3-effects.

    -webkit-transition-property: width height background-color font-size left top color;
    -webkit-transition-duration:1s;
    -webkit-transition-delay:1s;
    -webkit-transition-timing-function: linear;
    transition-property: width height background-color font-size left top color;
    transition-duration:1s;
    transition-delay:1s;
    transition-timing-function: linear;