javascript edit балончета

[BattleGrounds]

как мога да направя този скрипт балончетата да не се движат по екрана а да се появяват на рандом по екрана или ако знаете някой друг скрипт дайте :roll:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<a href="http://www.wysiwygwebbuilder.com" target="_blank"><img src="images/builtwithwwb5.gif" width="88" height="31" align="top" border="0" alt="Pablo Software Solutions" style="position:absolute;left:265px;top:533px;z-index:250"></a>
<div style="z-index:1">
<script language="JavaScript1.2">
<!--

var no = 1; // image number or falling rate
var speed = 2; // the lower the number the faster the image moves
var bubble = new Array();
bubble[0] = "bubble.gif"
bubble[1] = "bubble.gif"
bubble[2] = "bubble.gif"

var ns4up = (document.layers) ? 1 : 0;  // browser sniffer
var ie4up = (document.all) ? 1 : 0;
var ns6up = (document.getElementById&&!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 = 1800;

if (ns4up||ns6up) 
{
   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();
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 (ns4up) 
   {
      // set layers
      if (i == 0) 
      {
         document.write("<layer name=\"dot"+ i +"\" left=\"15\" top=\"15\" visibility=\"show\"><img src=\""+ bubble[j] + "\" border=\"0\"></layer>");
      } 
      else 
      {
         document.write("<layer name=\"dot"+ i +"\" left=\"15\" top=\"15\" visibility=\"show\"><img src=\""+ bubble[j] + "\" border=\"0\"></layer>");
      }        
   }
   else 
   if (ie4up||ns6up) 
   {                
      if (i == 0) 
      {
         document.write("<div id=\"dot"+ i +"\" style=\"POSITION: absolute; Z-INDEX: "+ i +"VISIBILITY: visible; TOP: 15px; LEFT: 15px; width:1;\"><img src=\"" + bubble[j] + "\" border=\"0\"></div>");
      } 
      else 
      {
         document.write("<div id=\"dot"+ i +"\" style=\"POSITION: absolute; Z-INDEX: "+ i +"VISIBILITY: visible; TOP: 15px; LEFT: 15px; width:1;\"><img src=\"" + bubble[j] + "\" border=\"0\"></div>");
      }
   }
   if (j == (bubble.length-1)) { j = 0; } else { j += 1; }
}

function BubbleNS() 
{  
   // Netscape main animation function
   for (i = 0; i < no; ++ i) 
   {  
      // iterate for every dot
      yp[i] -= sty[i];                
      if (yp[i] < -50) 
      {
         xp[i] = Math.random()*(doc_width-am[i]-30);
         yp[i] = doc_height;
         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]+pageYOffset;
      document.layers["dot"+i].left = xp[i] + 
      am[i]*Math.sin(dx[i]);
   }
   setTimeout("BubbleNS()", speed);
}

function BubbleIE_NS6() 
{  
   // IE main animation function
   for (i = 0; i < no; ++ i) 
   {  
      // iterate for every dot
      yp[i] -= sty[i];
      if (yp[i] < -50) 
      {
         xp[i] = Math.random()*(doc_width-am[i]-30);
         yp[i] = doc_height;
         stx[i] = 0.02 + Math.random()/10;
         sty[i] = 0.7 + Math.random();
         doc_width = ns6up?window.innerWidth-5:document.body.clientWidth;
         doc_height = ns6up?window.innerHeight-5:document.body.clientHeight;
      }
      dx[i] += stx[i];
      if (ie4up)
      {
         document.all["dot"+i].style.pixelTop = yp[i]+document.body.scrollTop;
         document.all["dot"+i].style.pixelLeft = xp[i] + am[i]*Math.sin(dx[i]);
      }
      else 
      if (ns6up)
      {
         document.getElementById("dot"+i).style.top=yp[i]+pageYOffset;
         document.getElementById("dot"+i).style.left=xp[i] + am[i]*Math.sin(dx[i]);
      }
   }
   setTimeout("BubbleIE_NS6()", speed);
}

if (ns4up) 
{
   BubbleNS();
} 
else 
if (ie4up||ns6up) 
{
   BubbleIE_NS6();
}
//
</script></div>
</body>
</html>