Hidden Link
Definition
Hidden links refers to links that are visible only to crawlers. Hidden links are usually stuffed with keywords.
Methods used to hide links
Links can be hidden by using an inconspicuous character (e.g. a dot) as anchor text.
Importance for SEO
Since hidden links are usually stuffed with keywords and their purpose is to manipulate the ranking, they are prohibited by search engines. If they find hidden links on a page, the website will be penalized.