function setCookie(NameOfCookie, value, expiredays)  
             {  
                var ExpireDate = new Date ();  
                ExpireDate.setTime(ExpireDate.getTime() + (expiredays * 24 * 3600 * 1000));  
                document.cookie = NameOfCookie + "=" + escape(value) +  
                ((expiredays == null) ? "" : "; expires=" + ExpireDate.toGMTString());  
             }
               
             function getCookie(NameOfCookie)  
             {  
                if (document.cookie.length > 0)  
                 {  
                     begin = document.cookie.indexOf(NameOfCookie+"=");  
                     if (begin != -1)     
                     {  
                         begin += NameOfCookie.length+1;//cookie值的初始位置  
                         end = document.cookie.indexOf(";", begin);//结束位置  
                         if (end == -1) end = document.cookie.length;//没有;则end为字符串结束位置 
                         document.write(document.cookie.substring(begin, end));
                         return unescape(document.cookie.substring(begin, end));
                     }  
                     }
                     return null;   
             }
              
             function delCookie (NameOfCookie)  
              {  
                  if (getCookie(NameOfCookie))
                   {  
                      document.cookie = NameOfCookie+"="+";expires=Thu, 01-Jan-70 00:00:01 GMT";  
                   }  
              }