Google has now become a public property. Hence to maintain its monopoly and to keep the trust of its shareholders Google is striving hard to optimize the quality of its search engines. Malpractices adopted by Adsense users are detected immediately and prompt actions taken like terminating your account.
Hence before starting your Adsense account you must know certain practices which are not acceptable.
Hidden texts. Using too small fonts or coloring the texts such that it blends with the background, loading the contents with keywords using CSS, or copying are some of the unacceptable acts like hiding links that are punishable.
Page cloaking. To get clicks some web owners use browser or bot sniffers to load the bots of unwanted pages which the visitors don’t really want.
Multiple submissions. Trying to submit more than one copy of your domain and pages, for instance, submitting a single Adsense URL as two different URLs. This is why auto submitters are avoided for people who are getting submissions. If your domain has already been submitted on any search engine then you can’t submit it again.
.Link farms. You must be careful about the links you paste on your page. If you post more than 100 links on a page then Google terms your site as link farm.
Selling page ranks. Putting your PR links on sale is different from selling ads or getting links.
Doorways. This is a process of loading a page using keyword ads in order to redirect the readers to another page, something like cloaking pages. Certain SEO companies now-days offer such services.
Search engines monitor your registry dates, domain IP’s, etc. If you maintain multiple domains or sub domains containing similar contents you might be caught
The above-mentioned policies are applicable to Google as well as other search engines hence ideal use of your Adsense account is best recommended.