Google AdSense allows webmasters to dynamically serve content relevant advertisements on web pages. If the visitor clicks one of the AdSense ads served to the website, the website owner is credited for the referral. Google's AdSense program essentially allows approved websites to dynamically serve Google's pay-per-click AdWord results.

Website maintenance related to AdSense is very easy and requires very little effort. Webmasters need only to insert a Google generated java script into the web page or website template.
Google's spider parses the AdServing website and serves ads that relate to the website's content. Google uses a combination of keyword matching and context analysis to determine what ads should be served. The java script calls the ad from Google and will ensure that ads are served each time a visitor goes to the web page.

Early on Google implemented a filtering system that allowed webmasters to prevent a specific domain's ads from being served on any websites in their account. Ad blocking meant that webmasters could prevent their competitor's ads from being dynamically served on their websites.

Google provides a wide variety of ad formats to match the most suitable option with a website. Webmasters can select from a handful of preformatted towers, inline rectangles, banners and buttons. The ad boxes can be modified by webmasters to resemble the website's color scheme. Examples of how different the various text boxes and color schemes appear on similarly themed sites can be viewed at:
http://www.ring-tone-software.com (scroll to the bottom)
http://www.ringtones-central.com (scroll to the bottom)
or
http://www.police-central.com (download left side)
http://www.police-supplies.com (scroll to the bottom)

Ads can be geo-targeted based on the visitor's location. Advertisements containing content in English, French, German, Italian, Dutch, Portuguese, Japanese, or Spanish are all available.

Channels
Google recently introduced channels, enhancing AdSense reporting.

When a channel is selected Google modifies the java script to include additional tracking. The additional tracking information allows webmasters to track a variety of metrics across their sites. Channels can be used to measure performance on various domains, differences in revenue with various ad sizes, or placement. By assigning each group of pages to a specific channel and comparing results in custom channel reports webmasters can work at increasing their AdSense revenue.

Optimizing
Google determines the content of the ads that are shown, webmasters serious about earning revenue from Google AdSense can use the following guidelines to optimize their website and ensure that targeted and relevant ads are served. If Google's spider has not crawled the site and determined the nature of the content, public service ads may be served. Public service ads will not accrue any AdSense revenue if clicked. As a result Google allows webmasters to designate alternate ads. Alternate ads allow webmasters to utilize the ad space in the event that Google is unable to serve targeted ads to the web page. By specifying an alternate image, HTML page, or ad server the advertising space can always being used effectively.

1.) Web page content on pages that ads are served should be static not dynamic.

2.) Ensure that the robot.txt does not prevent the web page from being spidered. Robots.txt file's will need to be removed or the following text will need to bedded to allow Google's content bot to crawl the site: User-agent: Media partners - Google

3.) If the website contains frames, select the ‘framed page’ checkbox when generating the ad layout code for that website.

4.) The body of the page and title of the page should contain contextual words that indicate a common theme on the web page.

Revenue Earned
Although Google doesn't disclose the exact revenue share or percentage that webmasters will earn, webmasters will receive a portion of the amount paid for clicks on Google ads on websites.

AdSense Conclusion:
Overall, Google AdWords can provide great supplemental income to webmasters with content sites. Implementing and maintaining Google AdSense program on a content site requires very little effort and can often bring a steady stream of additional revenue for webmasters.