これだけなら大丈夫です

<SCRIPT language="JavaScript1.2">
var no = 8;
var speed = 80;
STAR = new Array();
STAR[0] = "http://stat.ameba.jp/user_images/9d/e6/10067029526.gif";
STAR[1] = "http://stat.ameba.jp/user_images/73/50/10067033376.gif";
var dx, xp, yp; // coordinate and position variables
var am, stx, sty; // amplitude and step variables
var i, doc_width = 800, doc_height = 1800;
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();
myobj= new Array();
j = 0;
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 (i == 0) {
document.write("<img src='" + STAR[j] + "' border='0' name='dot"+ i +"' style='POSITION: absolute; Z-INDEX: "+ i +" display: block; TOP: 15px; LEFT: 15px;'>");
} else {
document.write("<img src='" + STAR[j] + "' border='0' name='dot"+ i +"' style='POSITION: absolute; Z-INDEX: "+ i +" display: block; TOP: 15px; LEFT: 15px;'>");
}
myobj[i]=document.getElementById("dot"+i);
if (j == (STAR.length-1)) { j = 0; } else { j += 1; }
}
function STAR_IE() {
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];
myobj[i].style.top = document.body.scrollTop+yp[i];
myobj[i].style.left = document.body.scrollLeft+xp[i] + am[i]*Math.sin(dx[i]);
}
setTimeout("STAR_IE()", speed);
}
STAR_IE();
// End -->
</SCRIPT>