how can I keep the focus on login button, when I enter the username / password?

so when the user hit the enter button the focus is on the login.

    <form id="form1" runat="server">
    <div>
        <div style="float: right">
            <asp:Button ID="NewUser" OnClick="NewUser_Click" Text=" New Users " runat="server"
                ToolTip="If you are a new user please click here" />
        </div>
        <br />
        <asp:Label ID="msgGeneral" BackColor="#006600" runat="server" ForeColor="White"></asp:Label><br />
        <br />
        <asp:Label ID="Label1" runat="server" Text="UserName:"></asp:Label>&nbsp;&nbsp;
        <asp:TextBox ID="UserName" runat="server"></asp:TextBox><br />
        <br />
        <asp:Label ID="lPassword" runat="server" Text="Password:  "></asp:Label>&nbsp;&nbsp;
        <asp:TextBox ID="Password" runat="server" ToolTip="Please enter password" TextMode="Password"></asp:TextBox><br />
        <br />
        <asp:Button ID="Login" runat="server" Text="Login" OnClick="Login_Click" />
        <br />
        <br />
        <br />
    </div>
    </form>