Code

<SCRIPT type=text/javascript>
  var snowmax=300
  var snowcolor=new Array("#AAAACC","#DDDDFF","#CCCCDD","#F3F3F3","#F0FFFF")
  var snowtype=new Array("Arial Black","Arial Narrow","Times","Comic Sans MS")
  var snowletter="*"
  var sinkspeed=0.9
  var snowmaxsize=22
  var snowminsize=8
  var snowingzone=1
  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) {
  marginbottom = document.body.clientHeight
  marginright = document.body.clientWidth
  }
  else if (ns6) {
  marginbottom = document.body.clientHeight
  marginright = window.innerWidth
  }
  else if (opera) {
  marginbottom = document.documentElement.clientHeight
  marginright = document.body.clientWidth
  }
  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
  snow[i].style.color=snowcolor[randommaker(snowcolor.length)]
  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
  snow[i].style.top=snow[i].posy
  }
  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]);
  snow[i].style.top=snow[i].posy

  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>