The practice of linking to pages deep within a Website rather than to just the homepage or main section pages. There is some increased risk of link rot (dead links forming) as a result of linking deep within sites as there is a higher chance of the older pages being changed, removed or archived. It is an important tool for Internet marketers seeking to improve their sites ranking for some long-tail phrases where a specific page is significantly more relevant to that result than the homepage. A viral marketing campaign might be used to build deep links to that specific page and ensure search traffic finds it’s way there.
Other site owners may be less keen on deep linking. A number of issues have arisen between newspapers over ownership of articles and Ticketmaster famously fell out with Microsoft over deep linking. Sometimes a site owner is significantly disadvantaged if users are directed straight to content instead of through the advertising and sign up process presented on their home page. Search engines can be encouraged to not index deep links using the robots.txt rules although this is a convention and not enforced in any way.