I am having the same problem as in this question.
I am using below code
<td>
<asp:HyperLink ID="HyperLink1" runat="server" NavigateUrl="test.aspx">Add Hotel Detail</asp:HyperLink>
</td>
<td>
<iframe id="frame1" style="height:800px; width:900px;" src="AdminControlPanel.aspx">
</iframe>
</td>
But with <asp:HyperLink>
,Target
attribute is not showing the frame id