chicagohh - 3:43 pm on Feb 19, 2009 (gmt 0)

I haven't seen too much evidence that validation makes a large impact on search ranking. I am not discounting that it can have an effect - just that it's often not large enough to see by itself.

Anyhow, I already rolled my own semantic analyzer. I use a lot of "small ball" tactics when it comes to my flavor of SEO and these semantic elements have the look of something that can make a difference -- when combined with other techniques.