Google Adsense Basics !
Google AdSense is an advertising program that was launched in the middle of 2003 by Google. Google acts as an intermediary between a vast number of advertisers and an equally impressive number of website owners. Advertisers sign up with Google and create text ads that they would like to be displayed. Google displays these ads on the results pages of searches that people conduct from Google.com.

The Google AdSense program allows these advertisements to show up on pages all over the internet. The webmaster simply places a special code in their page and Google AdSense takes care of the rest. Perhaps the most valuable aspect of the system is that robots (specialized computer programs that scan internet pages) analyzes pages that ads will be placed on to determine which ads are most relevant to the page's content.

Google AdSense Ad Formats & Sizes
Below listed are the standad Google AdSense Ad Formats & Sizes

Google AdSense Text Ads
Leaderboard (728 x 90)
Banner (468 x 60)
Button (125x125)
Half Banner (234x60)
Skyscraper (120x600)
Wide Skyscraper (160x600)
Small Rectangle (180x150)
Square (250 x 250)
Medium Rectangle (300 x 250)
Large Rectangle (336 x 280)

Google AdSense Image Ads
Leaderboard (728 x 90)
Banner (468 x 60)
Skyscraper (120x600)
Wide Skyscraper (160x600)
Small Square (200 x 200)
Square (250 x 250)
Medium Rectangle (300 x 250)
Large Rectangle (336 x 280)

Google AdSense Video Ads
Leaderboard (728x90)
Skyscraper (120x600)
Wide skyscraper (160x600)
Small Square (200x200)
Square (250x250)
Rectangle (300x250)
Large Rectangle (336x280)

Google AdSense Link Units
(120x90) Displays up to 5 links
(120x90_4) Displays up to 4 links
(160x90) Displays up to 5 links
(160x90_4) Displays up to 4 links
(180x90) Displays up to 5 links
(180x90_4) Displays up to 4 links
(200x90) Displays up to 5 links
(200x90_4) Displays up to 4 links
(468x15) Displays up to 5 links
(468x15_4) Displays up to 4 links
(728x15) Displays up to 5 links
(728x15_4) Displays up to 4 links

Google AdSense is a simple and low-risk way for publishers to quickly monetize their content. The pay-per-click ad (CPC) system has created an opportunity for anyone to instantly have advertising on their website, without the hassle of having to actively sell ad space. AdSense makes up a good portion of the advertising revenue for many websites, and other websites may use AdSense to earn the bulk of their revenues. Either way, AdSense is an excellent system for monetizing your content. With Google AdSense, one should never feel complacent because there's always a chance to improve earnings provided you are willing to experiment.

To display ads, a site must join Google's AdSense program. Joining is free, but not all sites are eligible to join. Once you're accepted, it is very simple to place the ads on your pages and to start generating revenue for your site. AdSense will serve ads that are generally very relevant to the content of a particular page. Google Adsense is the easiest way to attract advertisers from across the globe to your website/ blog. Just submit your blog or website to Google for approval and if their content team approves your content, you are ready to place contextual text ads on your websites. Every time a reader clicks an AdSense ad link, the AdWords advertiser pays Google a small fee and Google splits the revenue with you.

You can open a free Google Adsense account at: http://www.google.com/adsense/

The relevancy of ads placed by AdSense varies according to the page content, but most ads are usually very relevant to the page on which the ad is displayed. For example, the ads on this page should be related to the internet, advertising, and/or the Google AdSense program itself. Advertisers pay Google a certain amount for each time one of their ads are clicked. Google keeps a portion of this payment and passes on the rest to the owner of the website itself. Page views of the advertisements are irrelevant in terms of generating revenue in the program - commissions are only generated when internet users actually click on the ads themselves.

Google AdSense checks are sent out on a monthly basis. Many webmasters wait in anticipation of their checks since AdSense provides them a simple way to recoup some of the losses associated with posting websites on the internet. In some cases, webmasters can even make a profit using Google AdSense. Google deliver your cheque via courier or you can opt for a different payment option.

Some Tips to Increase Google AdSense Earnings:

1. Never modify the Google Adsense HTML code. If have trouble embedding AdSense code in your WordPress or Blogger template, take help of the AdSense support forums or send an email to your AdSense account manager.
2. Strictly follow the rules mentioned in Adsense policies. You will always earn more revenue from Adsense by playing it clean.
3. Never ask your friends or visitors to click on your Google ads. Google takes click fraud very seriously. Do not include incentives of any kind on your site for users to click on your ads. Don't label Google ads with text other than "sponsored links" or "advertisements."
4. Don't click on your own ads - Google is much smarter than you think and can discover invalid clicks through IP addresses, site navigation patterns, etc. If you working on a new design for your site, avoid reloading your pages (with AdSense) excessively. You can turn off AdSense temporarily and avoid invalid CPM impressions. Or you can use the unofficial Google Adsense Sandbox Tool that is accessible from Firefox, IE and other browsers to see what kind of Google ads will be served based on content (website address URL) or keywords.
5. Don't place ads in pop-up windows, error pages or even empty pages. Update: With the new AdSense policy change, you can probably place ads on 404 pages. Check with the AdSense support team.
6. Web visitors have a very short attention span and majority of them may simply leave after a quick glance. Their eyes follow a F pattern so you can get good results if the Google ads are placed in the areas colored red on the heat map. Sidebars and leaderboards at the top are often ignored.
7. For long articles, CTR will improve if you place ads somewhere in middle of the content or just where the article ends - when visitors are done reading the article, they may be looking for related resources.
8. Use Text Ads instead of Image Ads as users get more options and the payout is often higher. If you still want to display image ads (for CPM), consider ad formats like the 300x250 medium rectangle or the 160x600 wide skyscraper as they support also support rich multimedia and the new gadget ads.
9. Google Ads with no background color and no borders will always perform better. Make the border color and background color same as your page background color.
10. Always put ads above the main fold. Make sure that the ad unit with the highest clickthrough rate is the first instance of the ad code that appears in your HTML source. Since the first ad unit is always filled before the rest, you want to make sure that ad unit is located in the best placement on your page.
11. Go Wide - The large rectangle (336x280) is the best paying Adsense format especially for text ads. Try using the 336x280 large rectangle, 300x250 medium rectangle, or 160x600 wide skyscraper.
12. Maximum people think the search box is on the top right corner. So you know where to put it.
13. You can put upto 3 adsense units on a page. Try putting a large skyscraper on the right navigation sidebar of your website. That area is close to the browser scrollbar. You can also add 2 AdSense for search boxes and 3 adlink units.
14. Block low paying advertisers with Filters. Why to loose a visitor for an ad that will only pay you a cent. Use Overture or Google Adwords Keywords tool to discover keywords that are less popular with advertisers.
15. Monitor the AdSense performance of individual web pages with Google Analytics.