Cookies are browser-relatd, so use a browser that lets you delete cookies. Although why you should want to have to re-enter information all the time is beyond me. (That's what cookies are for - if you've been to a site and set things up the way you want them, some sites store that information on a cookie on your computer, instead of a database on theirs.)
So-called "private" or "anonymous" browsing also deletes cookies when you close the browser.