rails cookie missing for IE

I have a rails 2.1 application have the following code:
class CookieController < ApplicationController
  def index
     extra = cookies["extra"]
  end
end

<%= "index" %>
<script type="text/javascript">
    set_cookie();
    display_cookie();

    function readCookie(name) {
        var nameEQ = name + "=";
        var ca = document.cookie.split(';');
        for(var i=0;i < ca.length;i++) {
            var c = ca[i];
            while (c.charAt(0)==' ') c = c.substring(1,c.length);
            if (c.indexOf(nameEQ) == 0) return
c.substring(nameEQ.length,c.length);
        }
        return null;
    }
    function createCookie(c_name,value,expiredays)
    {
        var exdate=new Date();
        exdate.setDate(exdate.getDate()+expiredays);
        document.cookie=c_name+ "=" +escape(value)+
            ((expiredays==null) ? "" :
";expires="+exdate.toGMTString());
    }
    function set_cookie()
    {
        createCookie("extra","testbbb",100);
        createCookie("another","testanother",100);
        createCookie("ptheme","ccc",100);
    }
    function display_cookie()
    {
        alert(document.cookie)
        var x = readCookie('ptheme')

    }
</script>

The problem is that I can not see the cookie in controller when using
ie, I can not see the cookie when use firefox.
Any suggestion?
Thanks in advance