Glossary - D

database
An electronic filing system containing information that is usually highly organized and categorized. The benefit of electronic filing by means of a database is that specific information can easily be extracted according to given parameters. Search engines are essentially very large, searchable databases. Dynamic web pages typically rely on databases.

date range / date limit
Most of the major search engines allow users to limit search results to documents created / modified on / before / after a specified date.

dead link
A link to a page that no longer exists or has been moved to a different URL. Search engine spiders regularly respider pages in its index and removes dead links. Most search engines also offer ways for users to report dead links.

deep linking
The practice of linking to the inner pages of another web site - as opposed to linking to the homepage. Although the vast majority of site owners don't mind deep links to their sites, it should be noted that deep linking has potential legal ramifications.

de-listing
Referring to the removal of pages from a search engine index . De-listing can occur at the request of the site owner or a variety of other reasons. Most often, de-listing occurs when a page breaks one of a search engine's submission rules , making itself guilty of some sort of spamdexing . The Search Engine Yearbook contains comprehensive guidelines to help you avoid spamdexing and de-listing.

description
In the context of the search engines , the description refers to the descriptive text accompanied by a title and URL in the search results page. Some search engines take this description from the meta description while most generate their own from the page content. Directories often ask for a description when you submit your page.

description tag
An HTML tag that gives a general description of the contents of the page. This description is not displayed on the page itself, but is largely intended to help the search engines index the page correctly. Some search engines use the description found in the description tag on their SERP s. A growing number of search engines are completely ignoring the description tag. For a more detailed look at the description tag and other types of meta tags, please refer to the Search Engine Yearbook .

directory
A categorized collection of links to the web, usually compiled manually. Directories can either be general (to the entire web) like ODP or Topical like the Dotcom Directory. Although they cannot rival search engines for index size, the generally do offer higher quality search results , arrived at through some editorial selection process.

DNS
Domain Name Service / Domain Name System / Domain Name Server.
Every computer on the Internet has a unique number called the IP address . The IP address is almost like a telephone number, but it's hard to remember everyone's IP address. This is where DNS comes into play. The DNS is a static, hierarchical name service that makes it easier to remember web site addresses by allowing letters (the domain name) to be used instead of numbers. Translating the name back to the IP address is called "resolving" the domain.

DNS parking
A domain is set to be "parked" when it has been registered but not developed into a web site. The registrant pays the annual renewal fees to prevent the domain from falling into someone else's hands. DNS parking is typically done to protect trademarks. Domains registered for resale are usually also parked.

document streams
One of the problems that search engines have to deal with is that the web changes continuously. Their databases have to reflect new trends, news stories etc. They have to index document streams (e.g. news stories) that appear, tend to grow in intensity for a while ( burst ) and then gradually fade away.

domain / domain name
A sub-set of internet addresses. Top-level domains are divided into .com, .net, .org, .biz, .info, .gov and .edu. Apart from these there are also country-specific domain extensions like .ca, .com.au, .co.za, .fr etc. In SEO it is generally accepted that having a keyword -rich domain is beneficial. The Search Engine Yearbook contains a more detailed discussion of the importance of domain name selection in SEO , as well as what to look for when choosing a domain.

doorway page
Also known as bridge pages, bridging pages, entry pages and landing pages. Referring to a page designed to rank well for a selected keyword and redirect visitors to another, "real" page. Important here is that there are two kinds of doorway pages: those generated automatically based on a template and manually created keyword focused content pages (KFCPs). The first kind is considered spam and penalized by most search engines . The second is an important and usually very effective SEO technique. For a detailed discussion of doorway pages and all the do's and don'ts, please refer to the Search Engine Yearbook .

drill down
The action of clicking on links within a web site or directory , working through categories and sub-categories, in order to find specific information.

dynamic content
Web site content generated automatically, usually from a database and based on user actions / selections. Dynamic content typically changes at regular intervals, for example daily or each time the users reloads the page. SERP s are dynamically generated pages, changing depending on user input.