Onmouseover change background image of element

JavaScript
1

Hello,

I am trying to change the background image of an element onmouseover. Just can’t seem to get it going. Below is a link to the example that does nothing and the code.

http://www.servicewhale.com/backgroundSwitch.htm

Thanks for your help


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
	<head>
		<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
		<title>Untitled Document</title>
		<style>
			#wrapper {
				width: 150px;
			  height: 331px;
			  float: left;
				background: url('grid_box.gif') left top no-repeat;
			}
		</style>
		<script type="text/javascript">
			 function changeBG(x){
	        var NewBG = document.getElementById(x);
	
					var highLightBG = "grid_box_highlight.gif"
				
					NewBG.style.background = highLightBG;
	    }
		</script>
		
	</head>
	<body>
		<div id="wrapper" onmouseover="changeBG('wrapper')">
			
		</div>
		<div id="wrapper" onmouseover="changeBG('wrapper')">
			
		</div>
		<div id="wrapper" onmouseover="changeBG('wrapper')">
			
		</div>
	</body>
</html>
2

it should be


NewBG.style.background = 'url(' + highLightBG + ');';
3

Great! that did it thanks