//写cookies函数 
function setCookie(name,value,day)//三个参数，一个是cookie的名子，一个是值，另一个是保存的时间
{
    if(day>0)
    {
        var Days = day; //此 cookie 将被保存为指定的天数
        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();
    }
    else
    {
        if(getCookie(name)!=null)
            delCookie(name);
        document.cookie = name + "="+ escape (value);
    }
}
//读取cookies函数  
function getCookie(name)
{
    var arr = document.cookie.match(new RegExp("(^| )"+name+"=([^;]*)(;|$)"));
    if(arr != null) return unescape(arr[2]); return null;
}
//删除cookie
function delCookie(name)
{
    var exp = new Date();
    exp.setTime(exp.getTime() - 1);
    var cval=getCookie(name);
    if(cval!=null) document.cookie= name + "="+cval+";expires="+exp.toGMTString();
}

//function getCookie( name ) {     
//    var start = document.cookie.indexOf( name + "=" );   
//    var len = start + name.length + 1;   
//    if ( ( !start ) && ( name != document.cookie.substring( 0, name.length ) ) ) {         return null;     }   
//    if ( start == -1 ) return null;     var end = document.cookie.indexOf( ';', len );   
//     if ( end == -1 ) end = document.cookie.length;  
//        return unescape( document.cookie.substring( len, end ) ); 
//    }