Data Management Platform (DMP) -
A centralized system for gathering first-party data, integrating with third-party data, and applying this data to one’s advertising strategy. Advanced DMPs offer users the ability to create custom segments, forecast segment volumes, sync segments with other sources, overlay advanced analytics, and are often integrated with or part of DSP platforms.

Dedicated server -
A dedicated server is a type of Internet hosting solely for use by a single customer, account or domain name, where the client leases an entire server; i.e. a computer that only runs one type of server software, and is usually constructed according to the user’s specifications. Dedicated servers are appropriate for users that require lots of disk space or data transfer, as well as sites that are database intensive or have specific software requirements. Example: An Email server used by only one sender. Email usually goes out faster, and the server is more secure.

Deduplication (deduping) -
The process of removing identical entries from two or more data sets such as mailing lists. AKA merge/purge.

Delivered Email -
Number of Emails sent minus the number of bounces and filtered messages. A highly inexact number because not all receiving ISPs report accurately on which Email didn’t go through and why not.

Delivery tracking -
The process of measuring Email delivery rates by format, ISP or other factors and delivery failures (bounces, invalid address, server and other errors).

Demand Side Platform(DSP) -
A DSP is a technology platform through which buyers (Advertisers or Agencies) can plan, target, execute, optimize, and analyze digital media buying programs across 100% of the media plan. Through a DSP, the buyer can set targeting criteria, pricing, frequency, and other criteria governing the purchase of digital ad units. Advanced DSPs will provide additional capabilities to the buyer, including integration of various online and offline data sources, the ability to provision direct media buys (as opposed to just RTB), advanced optimization and decisioning capabilities, and creative tools.

Deploy -
The act of sending the Email campaign after testing.

DHTML (Dynamic Hypertext Markup Language) -
An extended set of HTML commands which are used by Web designers to create much greater animation and interactivity than HTML. 

Digest -
A shortened version of an Email newsletter which replaces full-length articles with clickable links to the full article at a Website, often with a brief summary of the contents.

Directory -
Specializes in linking to other Websites and categorizing those links. A Web Directory is not a Search engine, and does not display lists of Webpages based on keywords; instead, it lists Websites by category and subcategory. The categorization is usually based on the whole Website rather than one page or a set of keywords, and sites are often limited to inclusion in only a few categories. Web directories often allow site owners to directly submit their site for inclusion, and have editors review submissions for fitness.

Discrepancy -
This refers to the difference in recorded impressions between ad serving platforms which are involved in the process of publishing Online ads. It can be the basis for disputes between Publishers and ad serving agencies, in which Publisher’s own server metrics tend to be higher. The discrepancy tolerance threshold is 10%. Factors such as different impression calculation methods influence the level of reported discrepancy. 

Display advertising -
A form of Online advertising where an Advertiser‘s message is shown on a destination Webpage in a graphical format.

Domain name -
The unique name that identifies an Internet site. Every domain name consists of one top or high-level and one or more lower-level designators. Top-level domains (TLDs) are either generic or geographic. Generic top-level domains include .com (commercial), .net (network), .edu (educational), .org (organizational, public or non-commercial), .gov (governmental), .mil (military); .biz (business), .info (informational),.name (personal), .pro (professional), .aero (air transport and civil aviation), .coop (business cooperatives such as credit unions) and .museum. Geographic domains designate countries of origin, such as .ca (Canada), .us (United States),.fr (France), .uk (United Kingdom), etc.

Double opt-in -
A process that requires new list or survey panel joiners to take an action (such as clicking on an Email or ad embedded link to a personal confirmation page) in order to confirm that they do want to be on the list or panel. Sometimes interpreted incorrectly by some Email broadcast vendors to mean a new subscriber who does not opt-out of or bounce a welcome message.

DSL (Digital Subscriber Line) -
A high-speed dedicated digital circuit from a given location to the telephone company’s central office, using normal copper telephone lines. DSL provides a separate channel for voice and fax, which means that phone calls and faxes can be carried at the same time high-speed data is flowing across the line. DSL is a general term that includes several variations: ADSL (Asymmetric Digital Subscriber Line), ranging up to 1.5 Mbps; HDSL (High-bit-rate Digital Subscriber Line), 1.5 Mbps; SDSL (Single-line Digital Subscriber Line), 1.5 Mbps; VDSL (Very high-data-rate Digital Subscriber Line), ranging up to 2.3 Mbps; and RDSL (Rate Adaptive Digital Subscriber Line), various speeds.

Dynamic ad insertion -
The process by which an Online ad is inserted into a Webpage in response to a user’s request. Dynamic ad placement allows alteration of specific ads placed on a Webpage based on any data available to the placement program. At its simplest, dynamic ad placement allows for multiple ads to be rotated through one or more spaces. In more sophisticated examples, the ad placement could be affected by demographic data or usage history for the current user.

Dynamic content -
Email-newsletter content that changes from one recipient to the next according to a set of predetermined rules or variables, usually according to preferences the user sets when opting in to messages from a sender. Dynamic content can reflect past purchases, current interests or where the recipient lives.

Dynamic CPM (dCPM) -
The approach to winning ad traffic by increasing CPM bid by the necessary minimum in real time to outbid competition.

Dynamic pricing -
The purchase price for an ad impression that is determined via a real-time auction rather than a predetermined fixed rate.