please don't harrass or insult that website, but I recently browsed that website because I wanted to get a wallpaper, but then I realized the top bar was saying "Xenia suggests you get Firefox", wait what?? She wouldn't suggest that first of all, second, this means that the website knows if you are using Google or Firefox, so that can be a harmful addition. I will talk to the owner maybe, that is bad because all browsers can be good!! And that website is really pretty but I dislike that top bar.
They admitted they were slowing users with ad blockers, but many Firefox users reported experiencing the slowdown regardless of whether they used an ad blocker.
The article I linked, however, says that they couldn't get the delay to happen at all, so it's entirely possible it was just so poorly implemented that it was affecting people almost at random.