将下面的JavaScript代码加到< head >区就成了:


< Script Language="JavaScript" >
< !-- Begin
var no = 30;
//设定下落字符数量
var speed = 5;
//设定字符下落的速度
var ns4up = (document.layers) ? 1 : 0;
var ie4up = (document.all) ? 1 : 0;
//NETSCAP和IE两种不同浏览器各自进行定义
var s, x, y, sn, cs;
var a, r, cx, cy;
var i, doc_width = 800, doc_height = 600;
//设定字符下落区域为800*600
if (ns4up) {
doc_width = self.innerWidth;
doc_height = self.innerHeight;
}
else
if (ie4up) {
doc_width = document.body.clientWidth;
doc_height = document.body.clientHeight;
}
//NETSCAP和IE两种浏览器有别
x = new Array();
y = new Array();
r = new Array();
cx = new Array();
cy = new Array();
s = 8;
for (i = 0; i < no; ++ i) {
initRain();
//定义变量数组x, y, cx, cy, s
if (ns4up) {
if (i == 0) {
document.write("< layer name="dot"+ i +"" left="1" ");
document.write("top="1" visibility="show" >< font color="white" >");
document.write(",￥< /font >< /layer >");
}
else {
document.write("< layer name="dot"+ i +"" left="1" ");
document.write("top="1" visibility="show" >< font color="white" >");
document.write(", $ < /font >< /layer >");
}
}
//当i==0满足与否时，NETSCAP中的表现
else
if (ie4up) {
if (i == 0) {
document.write("< div id="dot"+ i +"" style="POSITION: ");
document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");
document.write("visible; TOP: 15px; LEFT: 15px;" >< font size="10" color="white" >");
document.write("￥< /font >< /div >");
}
else {
document.write("< div id="dot"+ i +"" style="POSITION: ");
document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");
document.write("visible; TOP: 15px; LEFT: 15px;" >< font size="10" color="white" >");
document.write(" $ < /font >< /div >"); //设定要下落的的字符（￥、$）及位置
}
}
//当i==0满足与不满足时，IE浏览器中的表现
}
function initRain() {
a = 6;
r[i] = 1;
sn = Math.sin(a);
cs = Math.cos(a);
cx[i] = Math.random() * doc_width + 1;
cy[i] = Math.random() * doc_height + 1;
x[i] = r[i] * sn + cx[i];
y[i] = cy[i];
}
function makeRain() {
r[i] = 1;
cx[i] = Math.random() * doc_width + 1;
cy[i] = 1;
x[i] = r[i] * sn + cx[i];
y[i] = r[i] * cs + cy[i];
}
function updateRain() {
r[i] += s;
x[i] = r[i] * sn + cx[i];
y[i] = r[i] * cs + cy[i];
}
function raindropNS() {
for (i = 0; i < no; ++ i) {
updateRain();
//定义变量数组 a , sn , cs , cx, cy, s
if ((x[i] < = 1) || (x[i] >= (doc_width - 20)) || (y[i] >= (doc_height - 20))) {
makeRain();
doc_width = self.innerWidth;
doc_height = self.innerHeight;
}
document.layers["dot"+i].top = y[i];
document.layers["dot"+i].left = x[i];
}
setTimeout("raindropNS()", speed);
}
function raindropIE() {
for (i = 0; i < no; ++ i) {
updateRain();
//在NETSCAP浏览器中的付值过程
if ((x[i] < = 1) || (x[i] >= (doc_width - 20)) || (y[i] >= (doc_height - 20))) {
makeRain();
doc_width = document.body.clientWidth;
doc_height = document.body.clientHeight;
}
document.all["dot"+i].style.pixelTop = y[i];
document.all["dot"+i].style.pixelLeft = x[i];
}
setTimeout("raindropIE()", speed);
}
if (ns4up) {raindropNS(); }
else
if (ie4up) {raindropIE(); }
//在IE浏览器中的付值过程
// End -- >
< /Script >