Some Definite Conclusions
There are quite a few interesting factors to this study that we were able to draw. The first, and most important, factor is that Google does not apparently give any weight to valid HTML. More importantly, Google apparently does not penalize invalid HTML at all. The study itself would almost lead us to believe that Google actually rewards invalid HTML with a higher ranking.
Secondary to the study, it seems that on-page optimization is no match for an established website. After just two days of being in the rankings, all of our test websites lost their top postions to The Lazy Wife. This happened in spite of the fact that our test websites had far more on-page optimization than The Lazy Wife for the keywords in question. The Lazy Wife, although still new, was still far more established, and thus won in the rankings.
Some Not So Definite Conclusions
I am not ready to admit that Google actually gives preference to invalid HTML, but the results seem to want to point us in this direction. The idea that Google actively rewards websites that put errors into their code simply does not make sense.
It is possible, however, that there is some other factor which we are not seeing here that occurs with a website that has invalid HTML. In other words, it may not be the improper HTML causing the sites to rank higher, but some other factor that we cannot see.
Another possibility could be that invalid HTML just happens to 'fit in' better with most reliable websites. The fact is, there are very few high-profile sites that can pass the muster of a validation test - could it be that Google is discounting sites with valid HTML as being 'too good to be true'? Is valid HTML a form of over-optimization?
I would lean towards disagreeing with this, but it is a possibility which should be discussed.
A Parting Shot at Google - and Compliments to MSN Search
Although Google does not seem to reward site owners for putting together a site with valid HTML - a goal of many well respected webmasters - MSN seems to be flawless. Out of curiousity I checked the results for relpepiblus lost and startnipol pin on MSN search and found that not only did MSN rank the sites with valid HTML higher - they kicked out the sites with invalid HTML.