Internal Links and Site Structure: Hierarchy

Today we’re moving on to the second part of our short series on internal linking Yesterday we talked about internal link anchor text. Today we’re going to talk about overall site hierarchy and how it affects your ability to rank.

Search engines analyze a lot of different factors of links to determine how much they benefit they give (if any). One of those factors is raw popularity, or PageRank. Building your site architecture to properly pass PageRank throughout the site is one of the most important SEO elements of your site navigation, and for very large sites good hierarchy will help your crawl and indexation rate as well.

The idea is that each page passes its PageRank (well, 85% of it anyway) through all the links on the page. You want to design your site to pass that PageRank in a way that is most beneficial for you, with the most juice flowing to the most important pages.

Basic Site Hierarchy

The basic site hierarchy that benefits your SEO efforts the most is to link from your home page to your most important category pages; then your category pages link to sub-category pages; then those sub-category pages link to product pages. Obviously you don’t have to have products, the bottom level can be anything from articles to specs to blog posts.

Image from SEOmoz

The point is that you have a pyramid-like linking structure within your site, with your home page then category pages at the top, and spreading out from there. Some truly large sites will have to add additional levels to the site in the sub-category pages area to best manage the quantity and diversity of pages. In general you want to do what’s best for usability, within a hierarchical structure. But you don’t want to go any further past 3 levels unless you have to, and you don’t want a flat structure either.

Understanding a Category level page

A lot of people misunderstand the category level, and don’t realize that they’re making tons of irrelevant pages into Category pages.

Any page that is linked to from your global navigation is a category page. You are telling Google that these are the most important pages on your site. In other words, every page of the site links to these pages. Keep your employment and other unimportant pages (pages that aren’t making you money) off of the top level if at all possible. Obviously some non-money pages (like contact info) will need to be at the category level for usability reasons.

Build around the hierarchy

Don’t just make a hierarchy of pages; design your site around that hierarchy. The category pages are the most important pages of your site, so be sure that the most important or most difficult to rank keywords exist on those category pages. If you sell sneakers you might have subcategories for brands, and product pages with different models — but that base category should be Sneakers (assuming that’s the keyword you’re targeting — it might be shoes or footwear).

Similarly your subcategory pages should be more important than the product (or sub-subcateogry) pages below it, because they are going to have more juice from the site structure.

Link juice flows uphill too

One of the great things about the hierarchical structure is that it allows very large sites to generate their own link juice and push it to the most important pages. The way this works is that every single page on the internet (that search engines know about) has some amount of PageRank — even if that page has no links to it.

Thus every product page of a giant site has some tiny amount of PageRank that it will pass through links — which means it’s passing through every link on the site navigation — to your category pages. As you keep adding pages, you keep adding a bit more juice to every category page!

Common Site Structure Mistakes

Here are some of the most common mistakes when building the structure of a website. Like all SEO elements, usability of your site has to come first and you must sometimes take SEO hits in the interest of usability, so don’t get too obsessed over maximizing every shred of internal structure. For example, you don’t want your Contact page to rank in the search engines, but you should certainly have a link to that in your site navigation!

  • Useless junk at the category level: far too many sites have garbage at the top navigation, category level. This is stuff like news, press releases, employment opportunities and about us pages all linked from the navigation. It makes sense that you may need to discuss this, but at the very least you should push all of that information under a single link with subcategories from that page. Remember, these are the most important pages on your site — make them your money pages!
  • Too many links: probably the absolute most common problem is trying to shove too many links into the navigation of your site — often through the use of dropdowns or flyouts. Remember, even if it’s a dropdown, Google sees it as a link. That means it’s a top Category page in your hierarchy — not a subcategory. The more categories you have, the less weight each of them holds. There really is a substantial benefit to limiting your categories down to what makes sense and limiting the number of links on the home page — we’ll get into this in more depth in the next article in this series. Just remember: navigation links are to category pages. The more category pages you create the more you’re creating a flatter structure, rather than a hierarchical one.