If you set it programmatically you can just call it like a variable (i.e. document.getElementById('image_1').style.top
). Otherwise, you can always use jQuery:
<html>
<body>
<div id="test" style="height: 100px;">Test</div>
<script type="text/javascript" src="jquery.min.js"></script>
<script type="text/javascript">
alert($("#test").css("height"));
</script>
</body>
</html>