Title contains invalid characters
Webmaster site title sanitize failed (webmaster-site-input) — disallowed characters or URL/script-like content.
Why this happens
Same rules family as Category contains invalid characters: no <>, javascript:, data:, or raw http(s):// in the title. Distinct from Title is too long.
Diagnose and fix
1. Use a plain site name without HTML or URLs.
2. Put the URL in the URL field only.
3. Retry add website.
4. See Could not add website.