Google adsense is pay-per click advertisement program owned by Google inc., according to Google, the purpose of adsense is to provide means of earnings for web publishers, adsense has been main source of income for many sites, Google adsense is the most popular pay-per click programe on the web, most publishers are not friendly with Google adsense policy, they end up loosing their adsense account and money, I recommend that you read and obey Google adsense policy carefully to get the best out of Google adsense, Most publishers are unable to get their adsense account approved by Google adsense due to the following reasons :
Duplicate Contents: publisher s that copy content from other site are not supported by Google adsense, this is mostly refer to as page issue by Google adsense.
Insufficient content: this is when the contents of your site is very short, it is recommended that you have up to 15-200 posts and 200 words in each posts, on your site before your Google adsense account is approved.
Duplicate Google Adsense Accounts: Publishers that create more than single google adsense accounts, has disobey google adsens policy, therefore their account will not be approved and their former account will be deactivated by google adsense, Google allow publishers to insert their google adsense code in any website, if publishers disobey and creat multiple google adsense accounts google have the right to disapprove it.
Website type: Google adsense does not support site that use abusive words and sites that contain adult contents , it is against Google adsense policy to create Google adsense account for this type of sites, Google will not approve your application for any invalid sites.