Sub-Sites
Parts of the Whole

Jakob Nielsen introduced the term "sub-site" in his September 1996 column The Rise of the Sub-Site. He defines a sub-site as "a collection of Web pages within a larger site that have been given a common style and a shared navigation mechanism." Think of sub-sites as distinct neighborhoods within one city's limits.

Nielsen has a few more rules of thumb for sub-sites:

• A sub-site should have its own main (home, front) page, different from the parent site's main page.

• Each page in a sub-site should link back to the sub-site's main page and the site's main page.

• A sub-site should have a global navigation system (discussed here) which is consistent with the parent site's.

• No sub-site should declare its independence from the parent site, since both benefit from the relationship.

• A sub-site needs its own local navigation system. Read on...

Local Navigation Systems

Local navigation systems offer another way to get around your site. They should be used in addition to, not instead of, other navigation systems: hierarchical, global, and ad hoc.

The example Morville and Rosenfeld use to explain local navigation systems is a product catalog sub-site. An online catalog will need different navigation options than the rest of the parent site: a popup menu of product categories, a search engine that finds keywords or concepts, a link to click that leads you to your online "shopping cart." As long as they're unique to the sub-site, it's local navigation.