Pour le code de la neige qui tombe !

<!-- DEBUT DU SCRIPT --><SCRIPT language=JavaScript>

  var snowsrc="Adresse de l'image"
  var no = 30;
  var ns4up = (document.layers) ? 1 : 0;
  var ie4up = (document.all) ? 1 : 0;
  var nn6up = (document.getElementById) ? 1 : 0;
  var dx, xp, yp;
  var am, stx, sty;
  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;
} else if (nn6up) {
    doc_width = self.innerWidth;
    doc_height = self.innerHeight;
}

  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;
    xp[i] = Math.random()*(doc_width-50);
    yp[i] = Math.random()*doc_height;
    am[i] = Math.random()*20;
    stx[i] = 0.02 + Math.random()/10;
    sty[i] = 0.7 + Math.random();
    if (ns4up) {
      if (i == 0) {
        document.write("<layer name=dot"+ i +" left=15 top=15 visibility=show><img src='"+snowsrc+"' border=0></layer>");
      } else {
        document.write("<layer name=dot"+ i +" left=15 top=15 visibility=show><img src='"+snowsrc+"' border=0></layer>");
      }
    } else if (ie4up || nn6up) {
      if (i == 0) {        document.write("<div id=dot"+ i +" style=\"POSITION: absolute; Z-INDEX: "+ i +"; VISIBILITY: visible; TOP: 15px; LEFT: 15px;\"><img src='"+snowsrc+"' border=0></div>");
      } else {
        document.write("<div id=dot"+ i +" style=\"POSITION: absolute; Z-INDEX: "+ i +"; VISIBILITY: visible; TOP: 15px; LEFT: 15px;\"><img src='"+snowsrc+"' border=0></div>");
      }
    }
  }

  function snowNS() {
    for (i = 0; i < no; ++ i) {
      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()", 10);
  }

  function snowIE() {
    for (i = 0; i < no; ++ i) {
      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()", 10);
  }

function snowNN6() {
    for (i = 0; i < no; ++ i) {
      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.getElementById("dot"+i).style.top = yp[i];
      document.getElementById("dot"+i).style.left = xp[i] + am[i]*Math.sin(dx[i]);
    }
    setTimeout("snowNN6()", 10);
  }
  if (ns4up) {
    snowNS();
  } else if (ie4up) {
 snowIE();
  } else if (nn6up) {
 snowNN6();
  }

</SCRIPT>

<!-- FIN DU SCRIPT -->