لماذا عندما اضع كود جافا سكربت لا يعمل

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  var snowsrc="http://i45.tinypic.com/2n9wdw2.jpg"
  var no = 7;
  var hidesnowtime = 0;
  var snowdistance="windowheight" ;


  var ie4up = (document.all) ? 1 : 0;
  var ns6up = (document.getElementById&&!document.all) ? 1 : 0;

  function iecompattest(){
  return (document.compatMode && document.compatMode!="BackCompat")? document.documentElement : document.body
  }

  var dx, xp, yp;
  var am, stx, sty;
  var i, doc_width = 800, doc_height = 10  ;
 
  if (ns6up) {
    doc_width = self.innerWidth;
    doc_height = self.innerHeight;
  } else if (ie4up) {
    doc_width = iecompattest().clientWidth;
    doc_height = iecompattest().clientHeight;
  }

  dx = new Array();
  xp = new Array();
  yp = new Array();
  am = new Array();
  stx = new Array();
  sty = new Array();
  snowsrc=(snowsrc.indexOf("mhmoudko.com")!=-1)? "http://i45.tinypic.com/2n9wdw2.jpg" : snowsrc
  for (i = 0; i < no; ++ i) {
    dx[i] = 0;         
    xp[i] = Math.random()*(doc_width-50);
    yp[i] = Math.random()*(doc_height-100);
    am[i] = Math.random()*20; 
    stx[i] = 0.02 + Math.random()/10;
    sty[i] = 0.7 + Math.random(); 
      if (ie4up||ns6up) {
      if (i == 0) {
 
      document.write("<div id="dot"+ i +"" style="POSITION:
absolute; Z-INDEX: "+ i +"; VISIBILITY: visible; TOP: 15px; LEFT:
15px;"><a href="http://www.6rbtop.com"><img
src='"+snowsrc+"' border="0"><\/a><\/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 snowIE_NS6() {
    doc_width = ns6up?window.innerWidth-100 : iecompattest().clientWidth-100;
 
    doc_height=(window.innerHeight &&
snowdistance=="windowheight")? window.innerHeight : (ie4up &&
snowdistance=="windowheight")?  iecompattest().clientHeight-100 : (ie4up
 && !window.opera && snowdistance=="pageheight")?
iecompattest().scrollHeight-50 : iecompattest().offsetHeight-50;
    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();
      }
      dx[i] += stx[i];
      document.getElementById("dot"+i).style.top=yp[i]+"px";
      document.getElementById("dot"+i).style.left=xp[i] + am[i]*Math.sin(dx[i])+"px";
    }
    snowtimer=setTimeout("snowIE_NS6()", 10);
  }

  function hidesnow(){
      if (window.snowtimer) clearTimeout(snowtimer)
      for (i=0; i<no; i++) document.getElementById("dot"+i).style.visibility="hidden"
  }
   

if (ie4up||ns6up){
    snowIE_NS6();
      if (hidesnowtime>0)
      setTimeout("hidesnow()", hidesnowtime*1000)
      }


</script>