- Physical Structure (e.g. menu, navigation bar)
- Flat structure
- Tree structure
- Logical Structure (e.g. quick links, internal links )
Flat structure is better than Tree structure due to the depth of the website.
However, for large website, using flat structure may probably reduce the Usability. To make use of logical structure such as making hot links/back links to hot pages in the homepage, not only it can enhance the SEO, but also increase the Usability.