Are Frameworks to be used as Parents W3C validated out of the box?

Hi Folks:

I AM A NEWB! My knowledge of programming is somewhat limited, but growing exponentially.

Up until now I have been a very casual user of WP, but now that I am launching my network of websites, I’m including a blog. My developers are building this for me, but I am doing as much groundwork as possible to select the right Framework/Parent on which we will create a child theme with my corporate look and feel, together with the feature set and flexibility I require.

I’ve pretty much decided to take full advantage of WP 3.0… no sense in working with yesterday’s version.

We will be adding to the blog a lot of navigation items, formatting and page structure to match the standard look and feel of the websites in my network, and these already pass W3C validation both for XHTML and CSS.

So, I’m a stickler for super clean, up-to-date code and W3C validation.

My humble and probably neophyte questions:

In choosing a framework, can I make the assumption that they all come out of the box W3C validated for both XHTML and CSS?

And, it is all the stuff that is added to and tinkered with in the Child Theme that causes a theme to fail validation?

I could really use some guidance here, if someone could lend a hand.

Thanking you all in advance,

Steve