Is there a plugin that will catch and/or stupid mistakes in my html when a post an entry on that my page will still validate (xhtml strict) ?

Try WC3Validator or Validate.

Does that help?

Donna

Just as a note, that will slow down your rebuld times phenomenally as it validates every single page as it rebuilds them.

There are a few plugins that simply keep you up with clean HTML, I'd browse through the cateogry listing at mt-plugins.org and see which one suits your needs best. =)