Quick question from reading Steve Krug's Don't make me think: A Common Sense Approach to Web Usability
What's the difference between pervasive navigation and primary navigation? Could someone give me an example each?
In short, primary navigation is the main hierarchical navigation, while pervasive navigation is always on the page.
For obvious reason there is a lot of overlap but it's not absolute. Let's say 99% of primary navigation is pervasive, and 50% of pervasive is primary. Analogy; 99% of cars are vehicles (some are scrap, or art or marketing) and 50% of vehicles are cars (many are bikes, trains etc.)
This is the one users are most interested in and are most likely/often going to use. Hierarchically, they are links to the top categories of the site. For example on Amazon.com, the primary categories are the departments:
Although it often IS placed at the top, it's a misconception that primary is the navigation at the top. Like you saw, Amazon uses a button in the top bar, but the menu actually expands more along the lefthand side of the screen than along the top. And Gmail and Hotmail for example use a more obvious side-by-side pane layout, where the primary hierarchical navigation is along the left side.
Although one could argue that the top bars (with links to other apps and your profile/settings) are primary, I'd disagree. You're here for mail, not other apps, so navigating your mail is the primary objective.
This is simply navigation that exists on every page. Among this are the primary navigation, but also links to user settings (not actual content), the search box (which is non-hierarchical) and links to stuff like copyright notices and EULAs (not really content either).
Looking at Amazon.com again, they have a substantial footer on every page: Which links to a lot of external pages, different languages, job openings, and all other sorts of things that aren't categories of products they sell.
Hotmail/Gmail also have a footer (though much smaller) with links to the terms of service. And as mentioned before, there are links to user settings and other apps always in the top bar. There are also semi-pervasive (on every page, but only if you have email(s) selected) buttons which aren't links but actions... so ignore that I even mentioned them?
Anyway; a lot of links that exist on every page, but aren't related to navigating the main content hierarchy.
Pervasive navigation. Pervasive navigation refers to nav links that are on almost all pages. They might be two-level tabs like in Amazon, or Windows-like dropdown/flyout menus. You can refer this for more research and navigation understanding. http://www.webstyleguide.com/wsg3/6-page-structure/3-site-design.html