JavaScript实现广告显隐切换功能

<script language="javascript"> 
<!-- 
function display(){ 
if(googlead.style.visibility == 'visible'){ 
googlead.style.visibility ='hidden' ; 
document.getElementById('words').innerHTML='关闭'; 
return true; 
} 
else{ 
googlead.style.visibility='visible'; 
document.getElementById('words').innerHTML='显示'; 
return false; 
} 
} 
//--> 
</script> 

<div id="googlead" style="margin-bottom:5px;width:728px;height:90px;float:left;visibility:visible">换客网广告...</div> 
<div id="myid" ><span id="words" onclick="return display()">关闭</span></div>