function jb51tuitan(){
if (getCookie('jb51popped')==''){
//要執行的代碼或一些操作
setCookie("jb51popped","ok"); //寫入cookies表示已經執行過了。 
alert("ok");
}
}
jb51tuitan()
function setCookie(name, value)    
{
    var argv = setCookie.arguments;
    var argc = setCookie.arguments.length;
    var expires = (argc > 2) ? argv[2] : null;
    if(expires!=null)
    {
        var LargeExpDate = new Date ();
        LargeExpDate.setTime(LargeExpDate.getTime() + (expires*1000*3600*24));
    }
    document.cookie = name + "=" + escape (value)+((expires == null) ? "" : ("; expires=" +LargeExpDate.toGMTString()));
}

function getCookie(Name)
{
    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
            return unescape(document.cookie.substring(offset, end))
         }
    else return ""
     }
}