Sitewide link

• A theme or template credit in the footer: "built with", "powered by", "site by".
• A partner or customer badge shown on every page.
• A link in the main navigation or the footer of your own site, pointing at your own pages.
• A blogroll or sponsor list in a sidebar.

A link repeated on ten thousand pages is not ten thousand links. Google consolidates it to roughly one link from that site, which is why buying a footer link on a large site buys far less than the page count suggests.

On your own site the same logic applies to internal links: a footer that links a hundred pages passes little to each, and it does not replace a contextual link from a page about the subject.

• Keep the footer to the sections a visitor actually looks for: the product, the pricing, the library, the legal pages, contact.
• Put the pages you want to rank in the body of the pages that discuss them, not only in the footer.
• A navigation of six to ten items is a decision about what matters; twenty is a decision not to decide.
• Breadcrumbs give a second path up the hierarchy and cost nothing.

• You paid for it, or traded for it, and it passes ranking. That is a link scheme, whatever the site.
• It carries an exact-match commercial anchor on every page, which is the pattern the Penguin update targeted.
• It comes from a network of sites that all link to each other, which is a private blog network by another name.
• It is your own footer stuffed with pages nobody asks for, which dilutes the links that matter and adds noise to every page.