I think I know the answer, but wanted to get some input on this .
We build sites for our company using a CMS, all our sites are built with HTML5. The seo/sem person who was brought in continues to insist that all of our site designs are "crap" because source order is all "wrong" - side bars and navs coming before main content areas, etc. This guy also thinks keyword metatags still matter too.. . I find myself in disagreement with him a lot. I'm no 'expert' in seo/sem, tracking rankings etc. but I do read a lot and try to keep up with this ever-shifting area, and I've been building websites since 1997, so I'm far from new at this.
So, does the source order really matter these days as far as indexing and ranking is concerned?
From what I'm reading, the answer is - not so much, if at all. Google indexes a lot more of a page than it once did (was it only 100kb of a page?). Google has evolved and is also 'smart' enough to get the relevant content on a page.