There is a page redirect occurring on some of the wiki pages. After 4 seconds, the browser is redirecting to a YouTube page.
Pages that I noticed are affected:
https://developer.mozllla.org/en-US/docs/Web
https://developer.mozllla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax
Pages that I noticed are NOT affected:
It appears that a stylesheet and some javascript code where added to the header in place of the “print” stylesheet.
Hello @chrond
thanks looks like someone added those line the page code
<script type="text/javascript">
function rrGo() {
// document.body.insertAdjacentHTML('beforeend', `<div id="rrContent"><iframe width="100%" height="100%" src="https://www.youtube-nocookie.com/embed/dQw4w9WgXcQ?autoplay=1&modestbranding=1" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>`);
location.assign('https://www.youtube.com/watch?v=dQw4w9WgXcQ');
};
document.addEventListener('DOMContentLoaded', function() { setTimeout(rrGo, 4000); }, {once: true});
</script>
and they remove the signin button but the last link is not affected
could you check this one @chrisdavidmills and could you also allow the sign in to be with something other than google and github
and have a nice day both of you
@justsomeone this is a prank — @chrond is attempting to rick-roll the entire MDN community 
If you look at the URLs they are pointing to, “mozilla” is spelled “mozllla” — it’s a different domain, into which they are loading the equivalent MDN content and then triggering the redirect after 4 seconds.
Quite clever; it had us fooled for a few minutes.
Oh good catch! I didn’t see that. I’ll just delete this post 
Edit: Or a mod can.
nice catch @chrisdavidmills
i thought that someone used the wiki option in annoying way
nice @chrisdavidmills
and have a nice day 
nice catch, bravo! 