D

Domain
A domain name is an identification label that defines a realm of administrative autonomy, authority, or control on the Internet, based on the Domain Name System (DNS).


Domain Name System (DNS)
An often-used analogy to explain the Domain Name System is that it serves as the "phone book" for the Internet by translating human-friendly computer hostnames into IP addresses. For example, www.example.com translates to 192.0.32.10.

Database
Data stored in a computer in such a way that a computer program can easily retrieve and manipulate the data.
Learn more about databases in our SQL tutorial

Database System
A computer program (like MS Access, Oracle, and MySQL) for manipulating data in a database.

DB2
A database system from IBM. Mostly for Unix and Solaris platforms.

DBA (Data Base Administrator)
The person (or the software) who administers a database. Typical task are: backup, maintenance and implementation.

DHCP (Dynamic Host Configuration Protocol)
An Internet standard protocol that assigns new IP addresses to users as need.

DHTML (Dynamic HTML)
A term commonly to describe HTML content that can change dynamically.
Learn more about DHTML in our DHTML tutorial

Dial-up Connection
In web terms: A connection to Internet via telephone and modem.

Discussion Group
See Newsgroup.

DNS (Domain Name Service)
A computer program running on a web server, translating domain names into IP addresses. Learn more about DNS in our Web Hosting tutorial

DNS Server
A web server running DNS.

DOM (Document Object Model)
A programming model for web page objects. (See HTML DOM and XML DOM)

Domain Name
The name that identifies a web site. (like: W3Schools.com)
Learn more about domains in our Web Hosting tutorial

DOS (Disk Operating System)
A general disk based computer operating system (see OS). Originally developed by Microsoft for IBM personal computers. Often used as a shorthand for MS-DOS.

Download
To transfer a file from a remote computer to a local computer. In web terms: to transfer a file from a web server to a web client. (see also Upload).

DSL (Digital Subscriber Line)
An Internet connection over regular telephone lines, but much faster. Speed may vary from 128 kilobit per second, up to 9 megabit per second.

DTD (Document Type Definition)
A set of rules (a language) for defining the legal building blocks of a web document like HTML or XML.
Learn more about DTD in our DTD tutorial

Dynamic IP
An IP address that changes each time you connect to the Internet. (See DHCP and Static IP).

Database
A data software file, containing many records, each of which contains the same set of fields, where each field contains a specific type of information.
Digital Certificates
The digital equivalent of positive identification, such as a driver's license. Issued by various certificate authorities, digital certificates are used to prove that a web site, or a visitor to a web site, is the entity or person they claim to be.
Digital Signatures
Digital signatures work just like paper-and-ink signatures, allowing document recipients to confirm the source of a document. Digital signatures are generated by digital certificates.
Dithering
When a color that is not browser safe is displayed, two browser safe colors are mixed (or alternated) to create the desired color. This is called dithering.
Domain Names
All servers on the Internet have a TCP-IP address that consists of a set of four numbers like 124.32.9.76 By assigning a name to the TCP-IP address - or vice versa - the Web becomes easier to use. URL addresses (domain names) are obtainable from many sources. Anyone can own a domain name. The real quest is finding one no one owns yet.
Download
To receive a copy of a file from another computer or web server using a modem.
Dynamic
A web document that is created from a database in real-time or "on the fly" at the same time it is being viewed, providing a continuous flow of new information and giving visitors a new experience each time they visit the web site.
DHTML (Dynamic HTML)
The next generation of HTML, the language that specifies exactly how text and images will be displayed on a web page. Dynamic HTML, developed by Netscape and the World Wide Web Consortium (W3C), is based entirely on industry-standard HTML and Java. New features in Dynamic HTML, such as absolute positioning, give designers and developers greater control over the look and feel of web pages.
Dynamic IP Addressing
Allows users to automatically locate Internet or intranet sites.
e-commerce (Electronic Commerce)
Conducting business online, including product display, online ordering, secure transactions and inventory management.

D Channel

The ISDN signaling channel. Runs at 16 or 64 Kbps.

Data transfer

In Web hosting, the total size of files transferred by an account in a month. Sites with a lots of graphics, downloads, or streaming audio or video and a lot of visitors will require plans with more available transfer.

Database

Data in a structured format stored on a web server. Most popular type is a relational database. The most common query (information retrieval) language for relational databases is SQL. Linux-based hosts most commonly include MySQL database and Windows NT-based hosts usually include Access or MS SQL databases.

Dedicated Server

Similar to co-location, except that you lease or rent hardware from a Web host. The main advantage over co-location is easier upgrade and usually better support. Getting a dedicated server or co-locating is necessary for sites that outgrow shared servers because they use a lot of bandwidth and resources or they require total control over software environment.

DES

Data Encryption Standard - an U.S. government approved cipher. It is easy to break in its simplest form, but used multiple times with key of at least 128 bits provides good security.

DHCP

(Dynamic Host Configuration Protocol). An automated way of obtaining an IP address in the Local Area Network.

Dial up

Dialup access is a way of connecting a computer to the Internet using a modem and the telephone line. It is rather slow and blocks the telephone line.

DNS

Domain Name System. Internet service that maps Internet domains into corresponding IP addresses. DNS database is distributed and replicated among many DNS servers, so when you change your domain's IP address, the changes take a while to propagate.

Domain name

Domain name is an easy-to-remember address that can be translated by DNS into server's IP address. Domain names are hierarchical. Domain's suffix indicates which TLD (top level domain) it belongs to, for example .com, .gov, .org, .net, or .jp. Recently ICANN (Internet Corporation for Assigned Names and Numbers) added several new TLDs, like .biz, .pro., and .museum.

DSL

Digital Subscriber Line. A better way of connecting a computer to the Internet using the telephone line. It's faster than the dialup and doesn't block the telephone line. However, it is more expensive because the special equipment is required.
DHCP
Abbreviation for Dynamic Host Configuration Protocol, an Internet standard protocol that allows IP addresses to be pooled and assigned as needed to clients.
Dial-up Connection
The most popular form of Net connection for the home user, this is a connection from your computer to a host computer over standard telephone lines.
Direct Connection
A permanent connection between your computer system and the Internet. This is sometimes referred to as a leased-line connection because the line is leased from the telephone company.
DNS
An acronym for Domain Name Server, DNS refers to a database of Internet names and addresses which translates the names to the official Internet Protocol numbers and vice versa.
Document
When used in reference to the World Wide Web, a document is any file containing text, media or hyperlinks that can be transferred from an HTTP server to a client program.
Document Window
This is the Web browser's scrollable window in which HTML documents can be viewed.
Download
To transfer to your computer a copy of a file that resides on another computer.
DSU
The abbreviation for Digital Services Unit, DSU replaces the modem in synchronous connections to the Internet.
Dynamic IP
In which the IP address may change (typically via DHCP) each time you log on to the Internet. See Static IP.