Activate button when Return is clicked?

[hpl]

I have a login. When I have entered username and password and hit return I wish to activate the button "Login" instead of the user needs to click the button. How can I solve that?

<table bgcolor="#efefef">
															<tr>
																<td colspan=2 class=overtext align=center>Login</td>
															</tr>
															<tr>
																<td><asp:label ID=lblBruger Runat=server>Indtast Brugernavn</asp:label></td>
																<td><asp:textbox id="txtBruger" cssclass=tastfelt runat="server" Width=80px></asp:textbox>&nbsp;<FONT SIZE="2" COLOR="red">*</FONT>
																<asp:RequiredFieldValidator ControlToValidate="txtBruger" Display=dynamic runat="server" id="RequiredFieldValidator1" /></td>
															</tr>
															<tr>
																<td><asp:Label ID=lblPassw Runat=server>Indtast Password</asp:Label></td>
																<td><asp:textbox TextMode="Password" cssclass=tastfelt id="txtPwd" runat="server" Width=80px />&nbsp;<FONT SIZE="2" COLOR="red">*</FONT>
																	<asp:RequiredFieldValidator ControlToValidate="txtPwd" Display=dynamic runat="server" id="RequiredFieldValidator2" />
																</td>
															</tr>
															<tr>
																<td colspan=2 align=center>
																	<asp:button cssclass="knap2" id="btnLogin" Text="Login" OnClick="Login_Click" runat="Server" /><br>
																	<asp:Label id="lblLoginMsg" runat="server" style="COLOR: red"></asp:Label>
																</td>
															</tr>
														</table>