如何设定网页在特定的时间弹出一个对话框？

如何设定网页在特定的时间弹出一个对话框？ 比如要在10月1日弹出“今天是国庆节，祝你节日快乐”。

脚本啊，很容易实现的

<SCRIPT language=javascript> <!-- calendar = new Date(); day = calendar.getDay(); month = calendar.getMonth(); date = calendar.getDate(); year = calendar.getYear(); if (year< 100) year = 1900 + year; cent = parseInt(year/100); g = year % 19; k = parseInt((cent - 17)/25); i = (cent - parseInt(cent/4) - parseInt((cent - k)/3) + 19*g + 15) % 30; i = i - parseInt(i/28)*(1 - parseInt(i/28)*parseInt(29/(i+1))*parseInt((21-g)/11)); j = (year + parseInt(year/4) + i + 2 - cent + parseInt(cent/4)) % 7; l = i - j; emonth = 3 + parseInt((l + 40)/44); edate = l + 28 - 31*parseInt((emonth/4)); emonth--; var dayname = new Array ("星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六"); var monthname = new Array ("1月","2月","3月","4月","5月","6月","7月","8月","9月","10月","11月","12月" ); document.write("<font color=FF0000>"+year +"年"); document.write(monthname[month]); document.write(date + "日"); document.write(dayname[day]+" "+"</font>"); // January(1月份节日，以下同。) if ((month == 0) && (date == 1)) document.write("元旦"); if ((month == 0) && (date == 10)) document.write("我的生日"); if ((month == 4) && (date == 1)) document.write("国际劳动节"); if ((month == 4) && (date == 4)) document.write("青年节"); if ((month == 5) && (date == 1)) document.write("国际儿童节"); if ((month == 11) && (date == 25)) document.write("圣诞节"); document.write(" </font>"); //--> </SCRIPT>