function getCookie(name)
    {   
        var offset,cookieValue;
        var search=name+"=";
        if(document.cookie.length>0)
        {
            offset=document.cookie.indexOf(search);
            if(offset!=-1)
            {
                offset += search.length;  
                end = document.cookie.indexOf(";", offset);  
                if (end == -1)
                    end = document.cookie.length;  
                cookieValue=unescape(document.cookie.substring(offset, end));
            }
        }
        return cookieValue;
    }
//name表示cookie的键的名字