Yes, you can definitely find this information
elsewhere but...what happens when you want to use a login control on a page and also use the default button property so when a user hits enter it submits the login control's button. Nothing, because you have no idea what the hell the ID of the submit button is.
Here is the workaround:
<asp:LinkButton ID="lnkbtn1" runat="server" />
<asp:Panel ID="pnlLogin" runat="server" style="display:none" CssClass="modalPopup"
DefaultButton="Login1$LoginButton" >
<div class="modaltext">
<label id="modalTextMessage" ></label>
<asp:Login ID="
Login1" runat="server" Width="246px" >
</asp:Login>
<asp:button id="btnCancel" runat="server" text="Cancel" />
</div>
</asp:Panel>