//写cookies函数
function SetCookie(name,value)//两个参数，一个是cookie的名子，一个是值
{
    var Days = 30; //此 cookie 将被保存 30 天
    var exp  = new Date();    //new Date("December 31, 9998");
    exp.setTime(exp.getTime() + Days*24*60*60*1000);
    document.cookie = name + "="+ escape (value) + ";expires=" + exp.toGMTString() +";path=/100class";//path是cookie的访问路径
}
//取cookies函数  
function getCookie(name)      
{
    var arr = document.cookie.match(new RegExp("(^| )"+name+"=([^;]*)(;|$)"));
    if(arr != null)
    return unescape(arr[2]);
    else
    return null;

}
//删除cookie
function deleteCookie(name)
{
    var exp = new Date();
    exp.setTime(exp.getTime() - 1);
    var cval=getCookie(name);
    if(cval!=null)
    document.cookie= name + "="+cval+";expires="+exp.toGMTString();
}