大神求助啊 鼠标移动图片

<html>
<head>
<title>鼠标移动图片</title>
<style type="text/css">
.drag{position:relative;cursor:hand}
</style>
</head><script language="JavaScript">
var dragapproved=false;
var z,x,y;
function move()
{
if(event.button==1&&dragapproved){
z.style.pixelLeft=temp1+event.clientX-x;
z.style.pixelTop=temp2+event.clientY-y;
return false;
}
}
function drags()
{
if(!document.all)
return
if(event.srcElement.tagName.toLowerCase()=="img")
{
dragapproved=true;
z=event.srcElement;
temp1=z.style.pixelLeft;
temp2=z.style.pixelTop;
x=event.clientX;
y=event.clientY;
document.onmousemove=move
}
}
document.onmousedown=drags;
document.onmouseup=new function("dragapproved=false"); 
</script><body>
<img src="img1.jpg" class="drag" onmousedown="drags()"/>
</body>
</html>
这哪里有错啊？？？不能移动的