关于函数控制多图层隐藏显现的问题~

当鼠标移动到文字时~控制layer3显示 layer2和layer1隐藏~
弄了一天，还是测试不成功，请请教，不胜感激~<style type="text/css">
<!--
#Layer1 {
position:absolute;
left:328px;
top:193px;
width:274px;
height:275px;
z-index:1;
background-color: #CC0000;
}
#Layer2 {
position:absolute;
left:550px;
top:382px;
width:138px;
height:118px;
z-index:2;
background-color: #3399CC;
}
#Layer3 {
position:absolute;
left:704px;
top:69px;
width:272px;
height:225px;
z-index:3;
background-color: #3300CC;
}
-->
</style>
<div id="Layer1"></div>
<div id="Layer2"></div>
<div id="Layer3" style="display:none"></div>
<a href="#" onmouseover="hide01("layer3","layer2","layer1")">sdfsdfsfdsf</a>
<script type="text/javascript">
function hide01(a,b,c) {
  document.getelementbyid(a).style.display="block";
  document.getElementById(b).style.display="none";
  document.getElementById(c).style.display="none";
}
function hide02() {
  document.getElementById("layer1").style.display="none";
}
</script>