There are many adwords advertisers who advertise their MFA[Made For Adsense] sites and try to make money normally called as arbitrage. There is a option in your Adsense accout which is called as the “Competitive Ad Filter” where in you can add all these bad sites or low paying advertisers and your website’s competitors. I have found a good list of advertisers who should be blocked in order to increase your eCPM and your overall total income.
There are many a times you would check your adsense account and find you have recieved 0.01$-0.03$/click and everyone would be interested in recieving 0.50$/click on an average, for which you either need to work on your adsense ads placement or else block these adverts which pay very low.
The Competitive Ad Filter enables you to block specific ads, such as competitors’ ads, from appearing on your pages. Entering a more general URL will block a wider range of ads; entering a more specific URL will block a smaller range of ads. For example, by entering a top level domain such as “example.com”, you’ll also block all ads that link to any sub-directories of that domain, like “forums.example.com”. Review the examples below to learn how you can create filters that will block only the range of ads you want.
Here are some advertisers which should be probably blocked using the “Competitive Ad Filter” option because many of these are just parked pages/MFA sites.
You can also generate your own adsense block list using this website