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Google Adwords and Adsense

In 2000 Google launched its Adwords system based on a similar idea. Google added the twist of ranking advertisements according to their popularity. If more people click on an advertisement further down the list it will be moved up even if other advertisers are bidding more for the query.

In the autumn of 2003 Google extended this system to third party websites calling the new program AdSense. Webmasters could include some Javascript code on their page and Google in turn would display adverts relevant to the content of the page. AdSense does this by indexing a page using its own robot called Mediabot. The User Agent string is:

Mediapartners-Google/2.1

When a user visits an AdSense enabled page that has not yet been indexed the AdSense code causes the page to be added to a queue. Mediabot then visits shortly afterwards. Using a separate robot ensures 'chinese walls' are maintained between search and advertising and ensure the robot is tailored towards the needs of content targeted advertising (CTA). The key to AdSense adverts are that they are unobtrusive and relevant to the content. Google uses technology called CIRCA acquired from Applied Semantics to help them understand the content of pages although adverts can be based on a single element, say the page title. Click through rates are monitored to control the quality of the adverts served.

The AdSense system gives webmasters a great deal of control over the look and feel of their adverts. A Web based control panel offers a set of layout formats: banner, skyscraper etc. with some predefined color schemes. The latter can be customized further by skilled webmasters to fit in with the design of the site. For each advert that a user clicks a percentage of the fee is passed to the website. Earnings vary for different keywords or even from day to day depending on what advertisers are bidding. Google does not allow members of the AdSense program to discuss their earnings but each click earns in the region of 20 to 40 cents with click through rates ranging from 2.5% to over 4%. Using the lower figures a site with a million page views per month would earn $5000. Unlike the Overture advertising program Google will accept sites with very low numbers of monthly page view, the only proviso is that a payout is made once earnings reach $100. AdSense generated a lot of excitement when it was launched in 2003 and has enabled many webmasters to at least cover expenses. More expert SEOers have been able to earn a living from AdSense alone.

Google Adwords and Adsense

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