The image you see above is a heat map of the old Google Adsense clickable region and the new one where the yellow color represents the active clickable region for Adsense ads. Google has recently redefined the clickable area for Google Adsense ads as reported by Google Blogoscoped.
Google previously did this to the ads in Google search results but now Google is planning to make this a universal feature for all Publishers.
This means that now you will get paid only for the clicks that are made within the region of the ad link or the ad url. Previously any click made within the range of the whole length of the ad block would be counted as valid and the Publisher used to get money for that but that theory will be a no-no from now onwards.
The main motif of Google behind this new change is to prevent invalid and accidental clicks which caused a lot of disturbance for the Advertisers but this will more likely kill the earnings of a lot of Publishers and the Click Through Rate is bound to fall.
Lets hope for the best 
we all know Google Adsense is our life.