What is cross-linking? Cross-linking refers to the purpose of using links to link one web page to another web page. This primer is a quick guide to understanding how a search engine determines which pages on a website are the most important by its internal links alone .
Most websites are primarily linked internally to each page in their website. Their hierarchy represents a confetti mess, an engine will crawl from one page to the next and will not be sure which page is the most important based on hierarchy alone. The following is an image of a poorly linked website:

Poorly Linked Website
Using the above linking structure, one can arrive at the importance of the pages only by analyzing the content of the pages and the context of the words used in the pages. However if the same words are used on every page, it goes without saying that one will not be able to differentiate between any of the pages.
On the converse, consider the image below:

Well Linked Website
Well constructed websites display a clear hierarchy. Each set of pages typically revolve around a very specific theme. A product page, details of the product page, support page, specific support portals for different products, etc.
An example of a good website following this specific theme methodology is Mobile Messaging Solutions. There are three top categories: products, solutions, technology. Click on one and there are additional subcategories within that categories and no links to other categories in other pages. Go all the way to the bottom and you have the sitemap. Headings are used properly, on first look and second look, one can tell that keywords have not been abused in the content of this site’s pages – in addition, every category possesses very clear information – this would be a good example of a site that caters to its users.