<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<script type="text/javascript">
function TimeToShow() {
var dt = new Date();
var la = document.getElementById("<%= Timer.ClientID %>");
la.innerHTML = dt.toLocaleTimeString();
window.setTimeout(TimeToShow, 1000);
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:label id="Timer" runat="server" text="Timer">
<asp:button id="btnStart" runat="server" text="Start"/>
</div>
</form>
</body>
</html>