My default Apache 404 page got a 38% of users will like it, 26 points for visually average, 20 for visual and 30 for clarity. After a few different URLs, my fail2ban kicked in, and the site complained about the URL being invalid. Fair enough.
Hilariously my blog (kn100.me) also got 38 percent and the site provides screenshots of other sites with similar scores, which were all 404/500 error pages... I thought my blog looked nice :(
Using my somewhat powerful but also flawed neuro net trained on over 20 years of intensive web usage gives your blog design a thumbs up. One suggestion is adding padding-top: 1em to the "Posts" heading to make it more clearly separated from the quick summary above it and more clearly related to the content below it.