Hi try like this..
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title></title>
<script src="JQuery.js" type="text/javascript"></script>
<style type="text/css">
.divclass
{
background-color: Red;
}
.divclickedclass
{
background-color: green;
}
</style>
<script type="text/javascript">
$(function () {
$('#div1,#div2,#div3').click(function () {
$('#div1,#div2,#div3').removeClass('divclickedclass').addClass('divclass');
$(this).removeClass('divclass').addClass('divclickedclass');
});
});
</script>
</head>
<body>
<form id="form1" runat="server">
<div id="div1" class="divclass" style="width: 100px; height: 100px; border: 1px solid red">
div1</div>
<div id="div2"class="divclass" style="width: 100px; height: 100px; border: 1px solid green">
div2</div>
<div id="div3" class="divclass" style="width: 100px; height: 100px; border: 1px solid blue">
div3</div>
</form>
</body>
</html>