If layout, and, what's worse, navigation, takes place in the beginning of HTML code, it sometimes is considered duplicate content by Google. So to be safe, it's better to make minimum layout in the beginning of the template, and start the content as soon as possible.
Hmm…interesting, but why? SE’s processing system can strip all HTML and look at pure text content. Granted, SE’s algos can look at layout properties such as bold, underline, etc, and incorporate it into evaluation mechanisms, but this is separate (or in addition to) looking at the text, so to me physical positioning of text and layout wouldn’t matter much. Is there any empirical evidence of this? [not trying to be dismissive, just curious]