And why is a flat site structure a good idea?
As a general rule the simpler a site’s structure, the ‘flatter’ it is.
Internal links are the links visitors use to navigate your website and find the stuff they’re looking for. A simple, flat site structure has a flat link structure, delivering a user-friendly experience that helps convert more visitors to sales.
When you have a flat directory structure, ie. it never takes more than a couple of clicks to get where you want to be, search engines will spider (explore) more of your site. Which means Google and co index and use more of the information in your pages to rank and rate your site. Because deep pages, buried layers down in sub-directories, are less likely to be spidered, a simple, flat site structure has considerable SEO benefits.
Not so flat: www.xyz.com/web/business/brighton/copywriting/about/copy.htm/
Nice and flat: www.xyz.com/copy.htm/