Any time I have a question about valid HTML I go to the Source. W3C has an invaluable tool for HTML . Becoming familiar with this will help you always create clean code.

Great find on that post. It lays it all out. As long as the silos are thin (not more than 2 layers beneath the home page) it can bring a benefit to adding extra ranking pages with minimal work comparatively. Rand talks about eliminating the bottom layer of the hierarchy to push the content up a level and make the resulting pages extremely stout. The major problem is always going to be the end of the chain. He calls them PageRank sinks.

Great question. While everyone has their schools of thought; both methods have their benefits. I tend to favor flat architecture with targeted cross linking. I guess you could call it a hybrid strategy. I begin with a totally flat architecture and silo where it makes sense for the rankings and the navigation for the user. It's all about logical grouping and don't forget the pages must all be link-worthy on their own. If the pages are all strong enough to generate links the problem tends to take care of itself.

Have you added Google Webmaster tools code and verified your site? This will give you fantastic insight into what is being crawled and if there are any dupe content problems present now.

Do you have an SEO plugin installed? Are canonicals set up? This would solve any problems for you if they exist.

***** OUR SCENARIO *****

We noindex pages, categories, and tags because we want our posts to rank on their own merit. We still assign categories and tags to posts for navigation internally but feel our posts stand on their own and are more of a benefit. Your experience and navigation may vary. We have never had a duplicate content problem yet and have operated our WP.org blog since before canonicals.

We are starting to see the comment spammers come out again with refined tactics because of the Panda Effect. Does your form allow comments on a blog? or deeper access? Bots and Hacks are always looking for a way in.

Nice Find on that article and Congrats on the Guru status