WHY PEOPLE FAIL IN ADSENSE
Not every Adsense publisher make success with Adsense. There are number of reasons that can drive you to failure in Adsense:
1. Is Your website content not good enough to satisfy your site visitors? If you have a website with few pages you can't hope to make success in Adsense. One of the important factor to make success in Adsense is to have lot of good and unique content. The main point is unique content. It's too hard to provide unique content every time. The information available to your site may also be available to others site. So what can you do? You have to provide the information in such a way that everybody loves to read it from your site. You have to try to make your site best on that topic.
2. Have you discussed multiple topics in your website? One website should concentrate in only one topic. If you have a sports site you cannot discuss about banking there. This will drive away your visitors who were interested in your sports site.
3. Have you chosen a topic that you have no actual interest in that? Choosing that type of topic will not help to update your content regularly. Your site visitors will lost their interest on your page when you can't provide any update.
4. You have chosen such a background and text color for your website that are not suitable for your visitors eyes. Though if your content is good your visitors will be wanting to quit your page as soon as they can for bad color combination of your website.
5. Do you fear to test with ad units? Don't fear to loose.Make test with different ad positions, ad formats and ad colors until you have found a good combination that satisfy you. When you make a change in ad combination observe it minimum 2-3 weeks. Sometimes a small change can change the whole thing a lot.
Read from Adsense blog how a small change can change a lot.
6. Are you getting a good number of visitors? Every one should try to get more traffic.