[GGCO]

In my opinion, it's not that important to be 100% validated. I used to be super anal about this, but have learned that it really doesn't matter as long as the site works and is consistent across all major browsers.

Obviously you want good HTML and CSS, so don't do anything dumb, but also realize that you don't need 100% validation in order for your site to work. An example of this would be not worrying about Youtube embed code not being validated.