[George]

My experience is that as soon as HTML code is generated automatically it is very common that it does not validate.

In our case it is Drupal. Even though you can edit your own templates in Drupal for example, it is embedded in code that Drupal generates. And yes, it is faulty. That also goes for Joomla and other CMSs as well.

Also the local GUI-s with which you can create website, beginning with Frontpage, Dreamweaver, Cold Fusion etc. it always was that way.

I personally write all my code manually and whenever possible validate it before I publish it.

If you want to use a program to generate your site I recommend to review the code after it is done and change those bugs manually if you can.