I have found an article about this on web and it is brought by Joel Comm (Dr.Adsense). I have extract part of the article for those who want to know more about Adsense. Here are some of tips by Joel Comm:
"AdSense Can Make You A Huge Heap Of Cash Lots of people make the mistake of believing that AdSense is only good for bringing a site a few extra pennies a month. Wrong! AdSense can fund your lifestyle - if you get it right."
"Junk Sites Get Junk Income But just because it's possible for a site to make a lot of money with AdSense, it doesn't mean that any site can make a lot of money with AdSense. Your site must have good content that can attract users on its own merit. There are a lot of different strategies available for producing good content for your site. You'll need to use them if you want to create the sort of site that makes real money."
For further reading visit here.
To know more about Joel Comm's website about adsense visit here.