Because it's there, it's fun and it's free. If you're reading this, you obviously have some interest in the internet. You don't even have to have your own site, although the more sites you use Google Adsense on, the more money you will make. For example, anyone can write a blog even if it's just your own opinion on something.

You can also make money referring other people to Google Adsense. By placing a referral button on your site you increase your earnings potential. When a publisher that you referred makes their initial $100.00 within 90 days of sign-up and is eligible for payout, your account will also be credited $100.00. Additionally, they must never have registered for a Google Adsense account before.

Don't be intimidated by the html code. It's already formatted. All you have to do is choose the language and kind of button you would like, and copy and paste the html code to your site. Look for the referral code and more information under Adsense support.