Site losing Google Pagerank not always a penalty

Shaun Anderson from Hobo Internet Search & Marketing Solutions blogs about a page that for some unknown reason didn't get any Pagerank love from Google although it should have, according to the site's general layout and PR value. He wonders if a penalty might have been put on that specific page, maybe due to the way it linked to other web sites.

My take on this starts with a little story: I started this blog a few days ago and had a dozen pages in google after 2-3 days, and was already getting a handfull of search engine traffic from the google SERPs. One day later all the pages but ONE were gone from the index. I didn't panic though. Not only does this blog not feed my family or anything like that, I also knew that I had not been a bad boy so it was highly unlikely that the mighty Google god had punished me in some way.

I figured it out rather quickly: I had installed some widget to improve the title tag of my blog. On sub pages, I wanted the post title to appear before the blog title and not the other way round. That worked well, but it turns out that the widget had also put some div tags right into the header section. Not good. I didn't notice first because after the widget install all browsers kept displaying the site without a problem. Sometimes the problem is something really easy, and not related to core SEO at all.

How does this relate to Shaun's problem you ask? Well, if a page has some truly wrong markup, then Google MIGHT just skip it or drop it, and that would definitely have an impact on the page's pagerank, too. I wouldn't say that Google is very sensitive as far as markup validity goes, but "displays well in the browser" is certainly not a good measurement for the Google-acceptance of HTML code.