I need to show cookie based content

1) On a few pages in my site, I want to show content based on if a cookie exists for the viewer. And, show different content if NO cookie exists for the viewer. 2) I want to add a form to add a username that will set the referrer cookie, if none exists. If they enter wrong username show html . 3) Add a link to automatically assign a random username, set the referrer cookie and refresh page so content shows based on referrer cookie from task 1 above.