Non-existent URLs does not redirect

On my Drupal 7 site, all non-existing URLs are not redirecting to 404 or any error page it should. Instead, it still remains showing its top parent URL. For example: the content www.mywebsite.com/mycontent-type/my-content is visible for any url like www.mywebsite.com/mycontent-type/my-content/aaaaa www.mywebsite.com/mycontent-type/my-content/bbbbbbbb etc. It is happening[…]