In a next step to provide advertisements to users that they are most likely to click, Google now asks for your interest categories, and displays Ads on any site that you visit (and has Adsense ads).
Your favorites/ interest categories are added to your browser cookie.
Therfore if you use more than one browser, you may need to configure ads for all the browsers.
Of course, if you use more than one computer, you may need to configure everywhere.
Where to select categories?