Zitat:This little plugin sends the correct HTTP status code on error pages.
By default, MyBB sends a "200 OK" response for every HTTP request.

Actually almost every search engines only understand HTTP status codes.
The problem is, that "200 OK" for Google & Co. means, everything is alright.

If a thread was deleted, MyBB shows an error message and sends "200 OK".
Google will never be informed about the deletion, so the link remains indexed.

With this plugin, the search engines will understood the error pages properly.