dsense is One of the Highest Paying program for Bloggers and Website owners. anyone can Optimize his/her site for these keywords.
CPC : Also known as Cost per Click which is the Amount of money you get when someone click on your Adsense Ad unit.Google Have different amount of Bucks for different keywords for every click depending upon your location on the Globe.You can Understand this by a Simple Example:
Car Insurance” Related Keywords have much More CPC than “Desktop Wallpapers” related Keywords.
This is the list of top or highest paying google keywords list

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