There was a system with dependent types that ruled out invalid html at compile time, even dynamically generated html (rather than a runtime error, you would get a compile error if your code did something wrong)

https://github.com/urweb/urweb

http://www.impredicative.com/ur/

Needless to say it wasn't very practical. But there was one commercial site written in it https://github.com/bazqux/bazqux-urweb (the site still exists but not sure if it's still written in ur/web)