AdSense is an ad serving program run by Google. Website owners can enroll in this program to enable text, image and, more recently, video advertisements on their sites. These ads are administered by Google and generate revenue on either a per-click or per-thousand-impressions basis. Google is also currently beta-testing a cost-per-action based service.
Google uses its search technology to serve ads based on website content, the user’s geographical location, and other factors. Those wanting to advertise with Google’s targeted ad system may sign up through AdWords. AdSense has become a popular method of placing advertising on a website because the ads are less intrusive than most banners, and the content of the ads is often relevant to the website.
Many sites use AdSense to monetize their content and some webmasters work hard to maximize their own AdSense income. They do this in three ways:
1. They use a wide range of traffic generating techniques including but not limited to online advertising.
2. They build valuable content on their sites which attracts AdSense ads which pay out the most when they get clicked.
3. They use copy on their websites that encourage clicks on ads. Note that Google prohibits people from using phrases like “Click on my AdSense ads” to increase click rates. Phrases accepted are “Sponsored Links” and “Advertisements”.
The source of all AdSense income is the AdWords program which in turn has a complex pricing model based on a Vickrey second price auction, in that it commands an advertiser to submit a sealed bid (not observable by competitors). Additionally, for any given click received, advertisers only pay one bid increment above the second-highest bid.
The underlying technology behind AdSense was derived originally from WordNet and Simpli, a company started by the founder of Wordnet — George A. Miller — and a number of professors and graduate students from Brown University, including James A. Anderson, Jeff Stibel and Steve Reiss. A variation of this technology utilizing Wordnet was developed by Oingo, a small search engine company based in Santa Monica founded in 1998. Oingo focused on semantic searches rather than brute force string searches. Oingo changed its name to Applied Semantics, which was then bought by Google for $102 million in April 2003, to replace a similar system being developed in house.
In May 2005, Google unveiled AdSense for feeds, a version of AdSense that runs on RSS and Atom feeds that have more than 100 active subscribers. According to the Official Google Blog, “advertisers have their ads placed in the most appropriate feed articles; publishers are paid for their original content; readers see relevant advertising — and in the long run, more quality feeds to choose from”.
AdSense for feeds works by inserting images into a feed. When the image is displayed by the reader/browser, Google writes the ad content into the image that it returns. The ad content is chosen based on the content of the feed surrounding the image. When the user clicks the image, he or she is redirected to the advertiser’s site in the same way as regular AdSense ads.
A companion to the regular AdSense program, AdSense for search lets website owners place Google search boxes on their pages. When a user searches the web or the site with the search box, Google shares any ad revenue it makes from those searches with the site owner. However, only if the ads on the page are clicked, the publisher is paid. Adsense does not pay publishers for mere searches.
As of September 2007, the HTML code for the AdSense search box does not validate as XHTML, and does not follow modern principles of website design:
* non-standard closing tags such as and
* the boolean (minimized) attribute checked rather than checked=”checked”
* presentational attributes other than id, class, or style, such as bgcolor and align
* a table structure used for purely presentational (non-tabular) purposes
* the font tag
The terms of the AdSense program forbid their affiliates from modifying the code, thus preventing these participants from having validated XHTML websites.
How AdSense works
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For contextual advertisements, Google’s servers use a cache of the page for the URL or the keywords in the URL itself to determine a set of high-value keywords. (Some of the details are described in the AdSense patent). If keywords have been cached already, ads are served for those keywords based on the AdWords bidding system.
For Site targeted ads, the advertiser can choose the page or sites it wants to display ads on and pays on a CPM basis (cost per thousand impressions).
For referrals, Google manages the subscriptions on a long term, to add money when the visitors either download the product of subscribe, that depend upon the sort of product.
For search, advertisements are added to the list of results and clicks on them make money.
Some webmasters create sites tailored to lure searchers from Google and other engines onto their AdSense site to make money from clicks. These “zombie” sites often contain nothing but a large amount of interconnected, automated content (e.g.: A directory with content from the Open Directory Project, or scraper sites relying on RSS feeds for content). Possibly the most popular form of such “AdSense farms” are splogs (“spam blogs”), which are centered around known high-paying keywords. Many of these sites use content from other web sites, such as Wikipedia, to attract visitors. These and related approaches are considered to be search engine spam and can be reported to Google.
MFA (Made For Adsense) is a site or page with little or no content, but filled with advertisements so users have no choice but to click on ads. Such pages were tolerated in the past, but due to complaints Google now disables such accounts.
There have also been reports of Trojans engineered to produce fake Google ads that are formatted to look like legitimate ones. The Trojan Horse apparently downloads itself onto an unsuspecting computer through a web page and then replaces the original ads with its own set of malicious ads.
Due to concerns about click fraud, Google AdSense has been criticized by some search engine optimization firms as a large source of what Google calls “invalid clicks” in which one company clicks on a rival’s search engine ads to drive up its costs. Some publishers have been blocked by Google, complaining that little justification or transparency was provided. Webmasters who publish Adsense can receive a lifelong ban without justification. Google claims they cannot “disclose any specific details” on clicks since it may reveal the nature of their proprietary click fraud monitoring system.
To help prevent click fraud, publishers of AdWords can choose from a number of click tracking programs. These programs will display detailed information about the visitors who click on the AdSense advertisements. Publishers can use that data to determine if they’ve been a victim of click fraud or not. There are a number of commercial tracking scripts available for purchase.
The payment terms for webmasters have also been criticized. Google withholds payment until an account reaches US$100, but many small content providers require a long time —- years in many cases —- to build up this much AdSense revenue. These pending payments are recorded on Google’s balance sheet as “accrued revenue share”. At the close of its 2006 fiscal year, the sum of all these small debts amounted to a little over US $370 million – cash that Google is able to invest but which effectively belongs to webmasters. However, Google will pay all earned revenue, even if smaller than 100 dollars, when the Adsense account is closed.
Google came under fire recently, after the official Google AdSense Blog showcased the French video-site Imineo.com. This site clearly violates Google’s AdSense Program Policies by displaying AdSense alongside explicit adult content. Typically, sites displaying AdSense have been banned from showing adult content.