<html>
<head>

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs
/jquery/1.4.0/jquery.min.js"></script>
</head>


<script type="text/javascript">
$(document).ready(function(){
$("button").click(function(){
$(".id100").height("200px");
$("#id200").width("200px");
});
});
</script>
</head>

<body>
<div class="id100" style="background:yellow;height:100px;width:100px">
HELLO</div>
<div id="id200" style="background:yellow;height:100px;width:100px">
W3SCHOOL</div>
<button type="button">Click me</button>
</body>

</html>