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Ad serving describes the technology and service that places advertisements on web sites. Ad serving technology companies provide software to web sites and advertisers to serve ads, count them, choose the ads that will make the website or advertiser most money, and monitor progress of different advertising campaigns.
An ad server is a computer server, specifically a web server, that stores advertisements used in online marketing and delivers them to website visitors. The content of the webserver is constantly updated so that the website or webpage on which the ads are displayed contains new advertisements—e.g., banners (static images/animations) or text—when the site or page is visited or refreshed by a user. The purpose of ad serving is to deliver targeted ads that match the website visitor's interest.
Ad serving also performs various other tasks like counting the number of impressions/clicks for an ad campaign and report generation, which helps in determining the ROI for an advertiser on a particular website.
Ad servers can be run locally or by third-party or remote ad servers. Local ad servers are typically run by a single publisher and serve ads to that publisher's domains, allowing fine-grained creative, formatting, and content control by that publisher. Remote ad servers can serve ads across domains owned by multiple publishers. They deliver the ads from one central source so that advertisers and publishers can track the distribution of their online advertisements, and have one location for controlling the rotation and distribution of their advertisements across the web.
The history of ad serving 
The first central ad server was released by FocaLink Media Services and introduced on July 17, 1995, for controlling the delivery of online advertising or banner ads. Although most contemporary accounts are no longer available online, the Weizmann Institute of Science published an academic research paper documenting the launch of the first ad server. The original motherboard for the first ad server, assembled in June 1995, is also preserved. Focalink relaunched the ad server under the name SmartBanner in February 1996. The company was founded by Dave Zinman, Noam N. Tepper and Jason Strober, and based in Palo Alto, California. In 1998, the company changed its name to AdKnowledge, and was purchased by CMGI in 1999. The AdKnowledge name was subsequently purchased by a company in Kansas City in 2004, which now operates under the brand name AdKnowledge.
The first local ad server was released by NetGravity in January 1996 for delivering online advertising at major publishing sites such as Yahoo and Pathfinder. The company was founded by Tom Shields and John Danner, and based in San Mateo, California. In 1998, the company went public on NASDAQ (NETG), and was purchased by DoubleClick in 1999. NetGravity AdServer was then renamed to DART Enterprise. In March 2008 Google acquired DoubleClick. Google has continued to improve and invest in DART Enterprise. The latest version of the product was renamed and shipped as DoubleClick Enterprise 8.0 on September 28, 2011.
Another central or remote ad server was introduced by David Stein at Burst! Media in January 1996 for controlling online advertising or banner ads. The company was founded by Jarvis Coffin, David Stein and Bob Hanna, and based in Katonah, New York. In 2006, the company went public on the London Stock Exchange's Alternative Investment Market (BRST).
Ad server functionality 
Common functions 
- Uploading advertisements and rich media.
- Trafficking ads according to differing business rules.
- Targeting ads to different users, or content.
- Tuning and optimization based on results.
- Reporting impressions, clicks, post-click & post-impression activities, and interaction metrics. ****
Advanced functions 
- Frequency capping so users only see messages a limited amount of time. (Advertisers can also limit ads by setting a frequency cap on money-spending)
- Sequencing ads so users see messages in a specific order (sometimes known as surround sessions).
- Excluding competition so users do not see competitors' ads directly next to one another. (Usually done by bidding on keywords)
- Displaying ads so an advertiser can own 100%
Ad targeting and optimization 
One aspect of ad serving technology is automated and semi-automated means of optimizing bid prices, placement, targeting, or other characteristics. Significant methods include:
- Behavioral Targeting - Using a profile of prior behavior on the part of the viewer to determine which ad to show during a given visit. For example, targeting car ads on a portal to a viewer that was known to have visited the automotive section of a general media site.
- Contextual Targeting - (also known as Semantic targeting) Inferring the optimum ad placement from information contained on the page where the ad is being served. For example, placing Mountain Bike ads automatically on a page with a mountain biking article.
- Creative Optimization - Using experimental or predictive methods to explore the optimum creative for a given ad placement and exploiting that determination in further impressions.
See also 
- Affiliate marketing
- Compensation methods
- Contextual advertising
- Internet marketing
- Landing page
- List of advertising networks
- Pay per click
- Pay per play
- Website monetizing
- View-through rate
- Marketing Land. "Study: For Display Ads Clicks Have “Nearly Zero” Correlation With Conversion". Retrieved 25 April 2012.
- Hyperlink Advertising Explodes on the World Wide Web, company press release
- Targeted Online Advertising, academic research
-  photograph, motherboard of first ad server
- First Advertising Server Launched On Internet; Focalink's Technology, Services and Information Creates Marketing Infrastructure for the Net, company press release
- New York Times contemporary news coverage
- NetGravity Launches AdServer, the Premier Advertising Management System Software for World Wide Web Publishers, company press release
- Advertisements on your Web Site, Press Release, USENET Newsgroupcomp.infosystems.www.announce
- "COMMERCIAL: Advertisements on your Web Site: Burst! Media". comp.infosystems.www.announces.