我是初学者也许方法很笨，但希望能帮解决下，谢谢
给你一个我曾经自己写的小效果吧，参考一下。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" " http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns=" http://www.w3.org/1999/xhtml">
<head>
<script type="text/javascript">
function moveBox(){
var box=document.getElementById("box");
var ch=(document.documentElement.scrollTop+document.documentElement.clientHeight-box.offsetHeight);
var cw=(document.documentElement.scrollLeft+document.documentElement.clientWidth-box.offsetWidth);
var top=parseInt(box.style.top);
var left=parseInt(box.style.left);
var speed=1;
//alert(document.getElementById("box").style.top);
if(top<ch && left==0){
top+=speed;
box.style.top=top;
}
else if(top==ch && left<cw){
left+=speed;
box.style.left=left;
}
else if(top<=ch && top>0 && left<=cw){
top-=speed;
box.style.top=top;
}
else if(top==0 && left<=cw){
left-=speed;
box.style.left=left;
}
//if(top==ch && left==cw){clearInterval(t);}
document.getElementById("zb").innerHTML="X:"+left+",Y:"+top;
//box.style.borderColor="rgb("+Math.random()*100+","+Math.random()*200+","+Math.random()*20+")";
box.style.borderColor="rgb("+top+","+left+","+Math.random()*20+")";
}
var t;
function startMove(){
t=setInterval("moveBox()",1);
}
function stopMove(){
clearInterval(t);
}
</script>
</head>
<body onload="startMove()">
<div class="box" id="box" style="position:absolute;top:0px;left:0px;border:2px solid green;background:#CCCCCC;text-align:center;">
<div id="zb" style="line-height:100px;width:100px;" onmouseover="stopMove()" onmouseout="startMove()"></div>
</div>
</body>
</html>
可以用swich ……case实现啊