Lille fejl i script !

Hej Eksperte...

Jeg har fundet dette script...:

<div id="staticbuttons" style="position:absolute;">
<img src="<%=man_URL%>/img/pil_op.gif" border="0" name="op" style="cursor:hand;" onmousedown="myspeed=-thespeed;MM_swapImage('op','','<%=man_URL%>/img/pil_op1.gif',1);" onmouseup="myspeed=0;MM_swapImgRestore();"><br>
<img src="<%=man_URL%>/img/pix.gif" border="0" height="5" width="1"><br><img src="<%=man_URL%>/img/pil_ned.gif" border="0" name="ned" style="cursor:hand;" onmousedown="myspeed=thespeed;MM_swapImage('ned','','<%=man_URL%>/img/pil_ned1.gif',1);" onmouseup="myspeed=0;MM_swapImgRestore();">
</div>

<script>
var Hoffset=250
var Voffset=80
var thespeed=2

var ieNOTopera=document.all&&navigator.userAgent.indexOf("Opera")==-1
var myspeed=0

var ieHoffset_extra=document.all? 15 : 0
var cross_obj=document.all? document.all.staticbuttons : document.getElementById? document.getElementById("staticbuttons") : document.staticbuttons

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

function positionit(){
var dsocleft=document.all? iecompattest().scrollLeft : pageXOffset
var dsoctop=document.all? iecompattest().scrollTop : pageYOffset
var window_width=ieNOTopera? iecompattest().clientWidth+ieHoffset_extra : window.innerWidth+ieHoffset_extra
var window_height=ieNOTopera? iecompattest().clientHeight : window.innerHeight

if (document.all||document.getElementById){
cross_obj.style.left=parseInt(dsocleft)+parseInt(window_width)-Hoffset+"px"
cross_obj.style.top=dsoctop+parseInt(window_height)-Voffset+"px"
}
else if (document.layers){
cross_obj.left=dsocleft+window_width-Hoffset
cross_obj.top=dsoctop+window_height-Voffset
}
}

function scrollwindow(){
window.scrollBy(0,myspeed)
}

function initializeIT(){
positionit()
if (myspeed!=0){
scrollwindow()
}
}
</script>

Problemet er bare når man trykke på knappen rykker billedet med pilen lige henholdsvis 3pixel ned og 3 pixel op...!

Hvordan kan dette laves om så billederne står stille...?