Javascript to Show Hide Div Visibility

<html>
<head>
<title>Javascript Show Hide Div Visibility</title>

<style type="text/css">
.divStyle {
width:200px;
height:100px;
margin:0px auto;
}
</style>

<script language="javascript" type="text/javascript">
function showHideDiv()
{
var divstyle = new String();
divstyle = document.getElementById("div1").style.visibility;
if(divstyle.toLowerCase()=="visible" || divstyle == "")
{
document.getElementById("div1").style.visibility = "hidden";
}
else
{
document.getElementById("div1").style.visibility = "visible";
}
}
</script>
</head>

<body>

<div id="div1" class="divStyle">
Show Hide Div visibility using Javascript DOM.
</div>

<center>
<input type="button" value="show hide div" onclick="showHideDiv()" />
</center>

</body>
</html>