How to use ScriptManager in asp.net ajax

ScriptManager
UsnigScriptManager.aspx

<%@ Page Language="C#" %>

<!DOCTYPE html>

<script runat="server">
    protected void Button1_Click(object sender, System.EventArgs e)
    {
        Label1.Text = "You clicked Button1 at:" + DateTime.Now.ToLongTimeString();
        Label1.ForeColor = System.Drawing.Color.Red;
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Ajax ScriptManager - How to use ScriptManager in asp.net ajax</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:DarkBlue; font-style:italic;">Ajax ScriptManager Example: How To Use ScriptManager</h2>
        <hr width="550" align="left" color="CornFlowerBlue" />
        <asp:ScriptManager 
            ID="ScriptManager1"
            runat="server"
            >
        </asp:ScriptManager>
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <br />
                <asp:Label 
                    ID="Label1" 
                    runat="server"
                    ForeColor="RosyBrown"
                    Font-Size="X-Large"
                    Text="This is a Label control for test Ajax feature"
                    >
                </asp:Label>
                <br /><br />
                <asp:Button 
                    ID="Button1"
                    runat="server"
                    Text="Get Button Click Time Using Ajax"
                    OnClick="Button1_Click"
                    Font-Bold="true"
                    ForeColor="DarkBlue"
                    Height="45"
                    />
            </ContentTemplate>                
        </asp:UpdatePanel>
    </div>
    </form>
</body>
</html>