SEO best practice can remind me of shifting sands. Perhaps nothing is set in stone at any given time. However, when it comes to layout of primary keywords you need to ensure that the chosen primary keywords will be the seen and spider-ed first. When the search engine Bots and Spiders visit your site they initially read the source code.
Think of this like the way we might read a the title of the book from the top downwards. In the SEO world there is a strong view that the Bots and Spiders place more relevance to keywords and phrases that are at the top of the page. Therefore, it is probably wise to place as much as possible of your primary page keywords and pages at the top of the page. It is also an idea to remove any potential obstacles, such as graphics and code.