Following HTML code snippet will help you to achieve it.
<form id="form1" runat="server">
<asp:Panel ID="pnlIndex"
runat="server"
DefaultButton="btnGo2">
<table cellpadding="0"
cellspacing="0"
border="0"
width="1002px"
height="100%"
id="tblMain"
align="center">
<tr align="left">
<td align="left">
<asp:TextBox runat="server"
Width="100px"
MaxLength="14"
ID="txtUserName"
AutoCompleteType="Disabled"
CssClass="TxtBox"></asp:TextBox>
</td>
</tr>
<tr align="left">
<td align="left">
<asp:Button ID="btnGo1" runat="server"
Width="30"
Text="Go1"
BackColor="#8b95ae"
OnClick="btnGo1_Click1"></asp:Button>
</td>
</tr>
<tr align="left">
<td align="left">
<asp:Button ID="btnGo2" runat="server"
Width="30"
Text="Go2"
BackColor="#8b95ae"
OnClick="btnGo2_Click1"></asp:Button>
</td>
</tr>
<tr align="left">
<td align="left">
<asp:Button ID="btnGo3" runat="server"
Width="30"
Text="Go3"
BackColor="#8b95ae"
OnClick="btnGo3_Click1"></asp:Button>
</td>
</tr>
</table>
</asp:Panel>
</form>
Explanation
As you can see in above code snippet, we have three buttons as
btnGo1, btnGo2, btnGo3.
Now say we like
to make btnGo2 as default button.
We created a
panel and declare the default button Id and put the remaining code inside the
pannel.
So now btnGo2 is the default for your page. You can change it by assigning other button
Id inside pannel tag.