the fact that you are considering to build a site in CMS (drupal) or using dreamweaver (static site) doesn't really have anything to do with HTML5, as of drupal, Its core still uses HTML4 (div div div) while some contrib or premium theme has already made an attempt to create a template with more HTML5 element on it, but still no Drupal site can claim 100% compliance to HTML5 due its core (up to Drupal 7) is not really HTML5 compliance.