adSense is an ad serving application run by Google Inc. Website owners can enroll in this program to enable text, image, and more recently, video advertisements on their websites. These advertisements are administered by Google and generate revenue on either a per-click or per-impression basis. Google beta tested a cost-per-action service, but discontinued it in October 2008 in favor of a DoubleClick offering (also owned by Google).Overview
Google uses its Internet search technology to serve advertisements based on website content, the user's geographical location, and other factors. Those wanting to advertise with Google's targeted advertisement system may enroll through AdWords. AdSense has become a popular method of placing advertising on a website because the advertisements are less intrusive than most banners, and the content of the advertisements is often relevant to the website.
Many websites use AdSense to monetize their content. AdSense has been particularly important for delivering advertising revenue to small websites that do not have the resources for developing advertising sales programs and sales people. To fill a website with advertisements that are relevant to the topics discussed, webmasters implement a brief script on the websites' pages. Websites that are content-rich have been very successful with this advertising program, as noted in a number of publisher case studies on the AdSense website.
Some webmasters invest significant effort into maximizing their own AdSense income. They do this in three ways:[citation needed]
1. They use a wide range of traffic-generating techniques, including but not limited to online advertising.
2. They build valuable content on their websites that attracts AdSense advertisements, which pay out the most when they are clicked.
3. They use text content on their websites that encourages visitors to click on advertisements. Note that Google prohibits webmasters from using phrases like "Click on my AdSense ads" to increase click rates. The 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. AdSense commands an advertiser to submit a sealed bid (i.e., a bid not observable by competitors). Additionally, for any given click received, advertisers only pay one bid increment above the second-highest bid.
AdSense for Feeds
In May 2005, Google announced a limited-participation beta version of 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."[5] AdSense for Feeds works by inserting images into a feed. When the image is displayed by a RSS reader or Web browser, Google writes the advertising content into the image that it returns. The advertisement 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 website in the same way as regular AdSense advertisements. AdSense for Feeds remained in its beta state until August 15, 2008, when it became available to all AdSense users.
XHTML compatibility
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 because of its use of * non-standard end tags, such as and , * the attribute checked rather than checked="checked", * presentational attributes other than id, class, or style — for example, bgcolor and align, * a table structure for purely presentational (i.e., non-tabular) purposes,1 and * the font tag.2 1: using a table structure for unintended purposes is strongly recommended against by the W3C, [7] but nevertheless does not cause a document to fail validation — there is currently no algorithmic method of determining whether a table is used "correctly" (for displaying tabular data or for displaying elements, that get proportionally wider or narrower when browser window resizes in width without active client side scripting). 2: the font tag is deprecated but does not fail validation in any XHTML standard[citation needed]. Additionally, the AdSense advertisement units use the JavaScript method document.write(), which does not work correctly when rendered with the application/xhtml+xml MIME type. The units also use the iframe HTML tag, which is not validated correctly with the XHTML 1.0 Strict or XHTML 1.0 Transitional DOCTYPEs. The terms of the AdSense program forbid its affiliates from modifying the code, thus preventing these participants from having valid XHTML websites. However, a workaround has been found by creating a separate HTML webpage containing only the AdSense advertisement units, and then importing this page into an XHTML webpage with an object tag.[8] This workaround appears to be accepted by Google.
How AdSense works
* The webmaster inserts the AdSense JavaScript code into a webpage.
* Each time this page is visited, the JavaScript code uses inlined JSON to display content fetched from Google's servers. * For contextual advertisements, Google's servers use a cache of the page to determine a set of high-value keywords. If keywords have been cached already, advertisements are served for those keywords based on the AdWords bidding system. (More details are described in the AdSense patent.) * For site-targeted advertisements, the advertiser chooses the page(s) on which to display advertisements, and pays based on cost per mille (CPM), or the price advertisers choose to pay for every thousand advertisements displayed. * For referrals, Google adds money to the advertiser's account when visitors either download the referred software or subscribe to the referred service. The referral program was retired in August 2008. * Search advertisements are added to the list of results after the visitor performs a search. * Because the JavaScript is sent to the Web browser when the page is requested, it is possible for other website owners to copy the JavaScript code into their own webpages. To protect against this type of fraud, AdSense customers can specify the pages on which advertisements should be shown. AdSense then ignores clicks from pages other than those specified.
