function killCookie(){
   var killDate = new Date();
     killDate.setMonth(killDate.getMonth()-1);
   var expirey = killDate.toGMTString();
    var userCookies = "user_name=delete;user_color=delete";
     document.cookie=escape(userCookies) + ";expires="+expirey;
   alert("Your cookie has been killed!");
 }