这就是我正在做的功能，我唯一想要改变的是让雪出现在一切的后面；所以它不在 div 之类的之上；我只是希望它出现在一切的背景中。这是代码。
<script type="text/javascript">
// Set the number of snowflakes (more than 30 - 40 not recommended)
var snowmax=35
// Set the colors for the snow. Add as many colors as you like
var snowcolor=new Array("#aaaacc","#ddddff","#ccccdd","#f3f3f3","#f0ffff")
// Set the fonts, that create the snowflakes. Add as many fonts as you like
var snowtype=new Array("Times","Arial","Times","Verdana")
// Set the letter that creates your snowflake (recommended: * )
var snowletter="*"
// Set the speed of sinking (recommended values range from 0.3 to 2)
var sinkspeed=0.6
// Set the maximum-size of your snowflakes
var snowmaxsize=30
// Set the minimal-size of your snowflakes
var snowminsize=8
// Set the snowing-zone
// Set 1 for all-over-snowing, set 2 for left-side-snowing
// Set 3 for center-snowing, set 4 for right-side-snowing
var snowingzone=1
///////////////////////////////////////////////////////////////////////////
// CONFIGURATION ENDS HERE
///////////////////////////////////////////////////////////////////////////
// Do not edit below this line
var snow=new Array()
var marginbottom
var marginright
var timer
var i_snow=0
var x_mv=new Array();
var crds=new Array();
var lftrght=new Array();
var browserinfos=navigator.userAgent
var ie5=document.all&&document.getElementById&&!browserinfos.match(/Opera/)
var ns6=document.getElementById&&!document.all
var opera=browserinfos.match(/Opera/)
var browserok=ie5||ns6||opera
function randommaker(range) {
rand=Math.floor(range*Math.random())
return rand
}
function initsnow() {
if (ie5 || opera) {
marginbottom = document.body.scrollHeight
marginright = document.body.clientWidth-15
}
else if (ns6) {
marginbottom = document.body.scrollHeight
marginright = window.innerWidth-15
}
var snowsizerange=snowmaxsize-snowminsize
for (i=0;i<=snowmax;i++) {
crds[i] = 0;
lftrght[i] = Math.random()*15;
x_mv[i] = 0.03 + Math.random()/10;
snow[i]=document.getElementById("s"+i)
snow[i].style.fontFamily=snowtype[randommaker(snowtype.length)]
snow[i].size=randommaker(snowsizerange)+snowminsize
snow[i].style.fontSize=snow[i].size+'px';
snow[i].style.color=snowcolor[randommaker(snowcolor.length)]
snow[i].style.zIndex=1000
snow[i].sink=sinkspeed*snow[i].size/5
if (snowingzone==1) {snow[i].posx=randommaker(marginright-snow[i].size)}
if (snowingzone==2) {snow[i].posx=randommaker(marginright/2-snow[i].size)}
if (snowingzone==3) {snow[i].posx=randommaker(marginright/2-snow[i].size)+marginright/4}
if (snowingzone==4) {snow[i].posx=randommaker(marginright/2-snow[i].size)+marginright/2}
snow[i].posy=randommaker(2*marginbottom-marginbottom-2*snow[i].size)
snow[i].style.left=snow[i].posx+'px';
snow[i].style.top=snow[i].posy+'px';
}
movesnow()
}
function movesnow() {
for (i=0;i<=snowmax;i++) {
crds[i] += x_mv[i];
snow[i].posy+=snow[i].sink
snow[i].style.left=snow[i].posx+lftrght[i]*Math.sin(crds[i])+'px';
snow[i].style.top=snow[i].posy+'px';
if (snow[i].posy>=marginbottom-2*snow[i].size || parseInt(snow[i].style.left)>(marginright-3*lftrght[i])){
if (snowingzone==1) {snow[i].posx=randommaker(marginright-snow[i].size)}
if (snowingzone==2) {snow[i].posx=randommaker(marginright/2-snow[i].size)}
if (snowingzone==3) {snow[i].posx=randommaker(marginright/2-snow[i].size)+marginright/4}
if (snowingzone==4) {snow[i].posx=randommaker(marginright/2-snow[i].size)+marginright/2}
snow[i].posy=0
}
}
var timer=setTimeout("movesnow()",50)
}
for (i=0;i<=snowmax;i++) {
document.write("<span id='s"+i+"' style='position:absolute;top:-"+snowmaxsize+"'>"+snowletter+"</span>")
}
if (browserok) {
window.onload=initsnow
}
</script>