Headings, heading hierarchy, and document outlines | 456 Berea Street
http://www.456bereastreet.com/archive/200901/headings_heading_hierarchy_and_document_outlines/

An article about html semantics and accessibility

"Recently my coworkers and I have been discussing HTML headings and heading hierarchy. This may not sound like something you need to spend a lot of time discussing, but there are some situations when it seems very difficult to find a solution without compromises."

Should logo be H1 and similar issues