I see “This site is under development” when visiting alexkozlov.com (or www.alexkozlov.com) which displays a page containing an <iframe> with a (possibly) malicious site.
This comes down to a DNS issue as the domain is not pointing to Netlify. You can choose to use Netlify DNS(docs) or configure DNS externally(docs).
There are a number of supports guides for DNS and custom domains compiled in this thread