function set_cookie(c_name, c_value, expiredays)
  {
    var exdate=new Date();
    exdate.setDate(exdate.getDate()+expiredays);
    document.cookie=c_name+ "=" +escape(c_value)+
    ((expiredays==null) ? "" : ";expires="+exdate.toGMTString());
  }

  function get_cookie (cookie_name)
  {
    var results = document.cookie.match ( '(^|;) ?' + cookie_name + '=([^;]*)(;|$)' );
    if ( results )
    	{
        return ( unescape ( results[2] ) );
      }else{
        return null;
    }
  }

  function delete_cookie(c_name) 
  { 
    set_cookie(c_name,"",-1); 
  }