<script language="JavaScript" type="text/JavaScript">
<!--
function showHideLayers(arg) {
    layerlength = leftmenulayer.length
    for(i=0; i<layerlength; i++){
        if(arg == i){
            leftmenulayer[i].style.visibility='visible'
        }else{
            leftmenulayer[i].style.visibility = 'hidden'
        }
    }
}
//-->
</script>

<a href="#" onMouseOver="showHideLayers(0)">1</a>
<a href="#" onMouseOver="showHideLayers(1)">2</a>
<a href="#" onMouseOver="showHideLayers(2)">3</a>

<div id="leftmenulayer" style="visibility: hidden;"> 
1
</div>
<div id="leftmenulayer" style="visibility: hidden;"> 
2
</div>
<div id="leftmenulayer" style="visibility: hidden;"> 
3
</div>