给一段下雪的代码。。。

<SCRIPT LANGUAGE="JavaScript1.2">

<!-- Begin
var no = 10; // snow number
var speed = 30; // smaller number moves the snow faster
var snowflake = "http://www.mambochina.net/modules/snow.png";

var ns4up = (document.layers) ? 1 : 0;  // browser sniffer
var ie4up = (document.all) ? 1 : 0;
var dx, xp, yp;    // coordinate and position variables
var am, stx, sty;  // amplitude and step variables
var i, doc_width = 800, doc_height = 600;
if (ns4up) {
doc_width = self.innerWidth;
doc_height = self.innerHeight;
} else if (ie4up) {
doc_width = document.body.clientWidth;
doc_height = document.body.clientHeight;
}
dx = new Array();
xp = new Array();
yp = new Array();
am = new Array();
stx = new Array();
sty = new Array();
for (i = 0; i < no; ++ i) {
dx[i] = 0;                        // set coordinate variables
xp[i] = Math.random()*(doc_width-50);  // set position variables
yp[i] = Math.random()*doc_height;
am[i] = Math.random()*20;         // set amplitude variables
stx[i] = 0.02 + Math.random()/10; // set step variables
sty[i] = 0.7 + Math.random();     // set step variables
if (ns4up) {                      // set layers
if (i == 0) {
document.write("<layer name=/"dot"+ i +"/" left=/"15/" ");
document.write("top=/"15/" visibility=/"show/"><img src=/"");
document.write(snowflake + "/" border=/"0/"></layer>");
} else {
document.write("<layer name=/"dot"+ i +"/" left=/"15/" ");
document.write("top=/"15/" visibility=/"show/"><img src=/"");
document.write(snowflake + "/" border=/"0/"></layer>");
   }
} 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;/"><img src=/"");
document.write(snowflake + "/" border=/"0/"></div>");
} else {
document.write("<div id=/"dot"+ i +"/" style=/"POSITION: ");
document.write("absolute; Z-INDEX: "+ i +"; VISIBILITY: ");
document.write("visible; TOP: 15px; LEFT: 15px;/"><img src=/"");
document.write(snowflake + "/" border=/"0/"></div>");
      }
   }
}
function snowNS() {  // Netscape main animation function
for (i = 0; i < no; ++ i) {  // iterate for every dot
yp[i] += sty[i];
if (yp[i] > doc_height-50) {
xp[i] = Math.random()*(doc_width-am[i]-30);
yp[i] = 0;
stx[i] = 0.02 + Math.random()/10;
sty[i] = 0.7 + Math.random();
doc_width = self.innerWidth;
doc_height = self.innerHeight;
}
dx[i] += stx[i];
document.layers["dot"+i].top = yp[i];
document.layers["dot"+i].left = xp[i] + am[i]*Math.sin(dx[i]);
}
setTimeout("snowNS()", speed);
}
function snowIE() {  // IE main animation function
for (i = 0; i < no; ++ i) {  // iterate for every dot
yp[i] += sty[i];
if (yp[i] > doc_height-50) {
xp[i] = Math.random()*(doc_width-am[i]-30);
yp[i] = 0;
stx[i] = 0.02 + Math.random()/10;
sty[i] = 0.7 + Math.random();
doc_width = document.body.clientWidth;
doc_height = document.body.clientHeight;
}
dx[i] += stx[i];
document.all["dot"+i].style.pixelTop = yp[i];
document.all["dot"+i].style.pixelLeft = xp[i] + am[i]*Math.sin(dx[i]);
}
setTimeout("snowIE()", speed);
}
if (ns4up) {
snowNS();
} else if (ie4up) {
snowIE();
}
// End -->
</script>