随滚动条移动的图层在html中可以移动,但在xhtml中却不可以,为什么?

<div id="floater" style="position:absolute; width:92px; z-index:1; height: 160">
<script language="JavaScript">
self.onError=null;
currentX = currentY =0;
whichIt = null;
lastScrollX =-10; lastScrollY = -100;
NS = (document.layers) ? 1 : 0;
IE = (document.all) ? 1: 0;
<!-- STALKER CODE -->
function heartBeat() {
if(IE) { diffY = document.body.scrollTop; diffX = document.body.scrollLeft; }
if(NS) { diffY = self.pageYOffset; diffX = self.pageXOffset; }
if(diffY != lastScrollY) {
percent = .1 * (diffY - lastScrollY);
if(percent > 0) percent = Math.ceil(percent);
else percent = Math.floor(percent);
if(IE) document.all.floater.style.pixelTop += percent;
if(NS) document.floater.top += percent;
lastScrollY = lastScrollY + percent;
}
if(diffX != lastScrollX) {
percent = .1 * (diffX - lastScrollX);
if(percent > 0) percent = Math.ceil(percent);
else percent = Math.floor(percent);
if(IE) document.all.floater.style.pixelLeft += percent;
if(NS) document.floater.left += percent;
lastScrollX = lastScrollX + percent;
}
}
<!-- /STALKER CODE -->
<!-- DRAG DROP CODE -->
function checkFocus(x,y) {
stalkerx = document.floater.pageX;
stalkery = document.floater.pageY;
stalkerwidth = document.floater.clip.width;
stalkerheight = document.floater.clip.height;
if( (x > stalkerx && x < (stalkerx+stalkerwidth)) && (y > stalkery && y < (stalkery+stalkerheight))) return true;
else return false;
}
function grabIt(e) {
if(IE) {
whichIt = event.srcElement;
while (whichIt.id.indexOf("floater") == -1) {
whichIt = whichIt.parentElement;
if (whichIt == null) { return true; }
}
whichIt.style.pixelLeft = whichIt.offsetLeft;
whichIt.style.pixelTop = whichIt.offsetTop;
currentX = (event.clientX + document.body.scrollLeft);
currentY = (event.clientY + document.body.scrollTop);
} else {
window.captureEvents(Event.MOUSEMOVE);
if(checkFocus (e.pageX,e.pageY)) {
whichIt = document.floater;
StalkerTouchedX = e.pageX-document.floater.pageX;
StalkerTouchedY = e.pageY-document.floater.pageY;
}
}
return true;
}
function moveIt(e) {
if (whichIt == null) { return false; }
if(IE) {
newX = (event.clientX + document.body.scrollLeft);
newY = (event.clientY + document.body.scrollTop);
distanceX = (newX - currentX); distanceY = (newY - currentY);
currentX = newX; currentY = newY;
whichIt.style.pixelLeft += distanceX;
whichIt.style.pixelTop += distanceY;
if(whichIt.style.pixelTop < document.body.scrollTop) whichIt.style.pixelTop = document.body.scrollTop;
if(whichIt.style.pixelLeft < document.body.scrollLeft) whichIt.style.pixelLeft = document.body.scrollLeft;
if(whichIt.style.pixelLeft > document.body.offsetWidth - document.body.scrollLeft - whichIt.style.pixelWidth - 20) whichIt.style.pixelLeft = document.body.offsetWidth - whichIt.style.pixelWidth - 20;
if(whichIt.style.pixelTop > document.body.offsetHeight + document.body.scrollTop - whichIt.style.pixelHeight - 5) whichIt.style.pixelTop = document.body.offsetHeight + document.body.scrollTop - whichIt.style.pixelHeight - 5;
event.returnValue = false;
} else {
whichIt.moveTo(e.pageX-StalkerTouchedX,e.pageY-StalkerTouchedY);
if(whichIt.left < 0+self.pageXOffset) whichIt.left = 0+self.pageXOffset;
if(whichIt.top < 0+self.pageYOffset) whichIt.top = 0+self.pageYOffset;
if( (whichIt.left + whichIt.clip.width) >= (window.innerWidth+self.pageXOffset-17)) whichIt.left = ((window.innerWidth+self.pageXOffset)-whichIt.clip.width)-17;
if( (whichIt.top + whichIt.clip.height) >= (window.innerHeight+self.pageYOffset-17)) whichIt.top = ((window.innerHeight+self.pageYOffset)-whichIt.clip.height)-17;
return false;
}
return false;
}
function dropIt() {
whichIt = null;
if(NS) window.releaseEvents (Event.MOUSEMOVE);
return true;
}
<!-- DRAG DROP CODE -->
if(NS) {
window.captureEvents(Event.MOUSEUP|Event.MOUSEDOWN);
window.onmousedown = grabIt;
window.onmousemove = moveIt;
window.onmouseup = dropIt;
}
if(IE) {
document.onmousedown = grabIt;
document.onmousemove = moveIt;
document.onmouseup = dropIt;
}
if(NS || IE) action = window.setInterval("heartBeat()",1);
</script>
<a href="/dreamweaver/"><img src="1.gif" width="90" height="90" border="0"></a>
</div>