Why doesn't Google approve my site for ads?
Do you have enough content on your website?
Google doesn't approve sites with 1-2 pages of content. They need more pages of content, so that they know exactly what your site is about and be able to display only ads related to it.
Then, is your site built on a registered domain?
Google have changed their politics and don't accept anymore (since late 2008) free domains. So, make sure you register your domain.
Doesn't your topic break Google AdSense's Program Policies?
Before you submit your site to Google AdSense, make sure you read AdSense's Content Guidelines. They do not accept violent, adult, casino-related content...
Do you have a navigation menu or a site map?
You must have a navigation menu or a site map, so that your visitors can easily navigate through your website. Many approval requests have been rejected by Google AdSense due to lack of a site map or a menu.
If you accomplish all these things, you should have no problem in getting accepted by Google AdSense.
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