I have been doing some homework on cookie, how they work, etc. I was wondering, can you make a cookie that uses JS that can alter the appearence of a website? Can a cookie alone, once installed on the browser, do this or does there need to be more code to make it work? I found this script which sounds a little like what im talking about: http://javascript.internet.com/cookies/remove-ads.html
The cookie itself is just a small piece of information, it can't do nothing alone. What you need is to read it's value either on the server side, or on the client side using javascript, and make the necessary changes accordingly.
cookie is just a file in which you can store information about the session or the user etc. You can do a lot of stuff with this information.