I have just found that my site stefantsov.com can not be opened from Russia. Since I'm not doing anything bad, this was a surprise for me. After digging a bit, thanks to +Fedor, I was able to find the reason behind the blocking.

For stefantsov.com I'm using Cloudflare CDN to deliver resources faster all around the world, reduce server bandwidth, get some free optimizations, etc. Cloudflare effectively hides my real IP, delivering all content itself. Currently site's IP resolves to 141.101.116.129: CLOUDFLARE-EU. In russian blacklist there is some hentai site, that is using Cloudflare as well, resolves to same IP address. It got blocked few days ago, which effectively blocks my site as well.

gl hf gg wp no re, да здравствует великий российский файрвол, guys.
[Random In Soviet Russia joke]