First of all know the meaning of the word CPC, LCP, MFA.
CPC- Cost Per Click
LCPC- Low Cost Per Click
MFA-Made For Ad
I think you know about CPC and LCPC but many of you don't know MFA. There are few banners on the internet which are made only for ads. This appears repeatedly on your site where you pasted the adsense code. This ads are seldom clicked by visitors. But the advertisers are getting benefit again and again it appears on your site. So you must stop these ads by blocking them in your adsense account.
One question is arising that how will you become sure that it is MFA . So I am giving one trick here. Go to keywordspy.com and paste the address of this site then you will notice that it is paying very low CPC. To know the address of the MFA right click on this ad . Copy the link address and paste it in notepad. See carefully the code you will find a word adurl after that you will find the address of the mfa site.