Small correction to my own reply: NIP-32 lists `e`, `p`, `a`, `r` and `t` as the targets and describes them as "events, people, relays, or topics respectively". So by the text, `r` means relays, not web pages. Pointing an `r` tag at a website URL would be stretching the spec. For page reviews you'd want to write that down in your own namespace's rules, or propose it as an extension, so other clients read it the same way. The count above stands.