Vanishing Excel tab issue (ASP.net)

Hi All,

I have created a small demo web application for you all to see the bug.
The start page is frameset.htm.

To reproduce the error, click on the Excel1(Hyperlink button) and then Excel2(Hyperlink button2)
(these button will displays excel documents one after another). You will see the bug in the second excel document.

If you instead click Excel1,Image(Hyperlink button which displays image) and then Excel2. This bug will not be found.

Here are the codes:
FrameSetPage.htm (This is the start page)

<frameset name="fr_main" id="fr_main" rows="*,50%"      frameborder="1">
		<frame name="fTop" id="fTop"    src="FrameTop.aspx" frameborder="1" >
		<frame name="fBottom" id="fBottom"   frameborder="1" >
	</frameset>

FrameTop.aspx

<form id="form1" runat="server">
        <asp:HyperLink ID="LinkButton1" runat="server">Excel1</asp:HyperLink>
                <asp:HyperLink ID="LinkButton2" runat="server">Image</asp:HyperLink>
                        <asp:HyperLink ID="LinkButton3" runat="server">Excel2</asp:HyperLink>
      
    </form>

FrameTop.aspx.cs

protected void Page_Load(object sender, EventArgs e)
    {
        
        LinkButton1.NavigateUrl = "FrameBottom.aspx?id=1" ; 
        LinkButton1.Target = "fBottom";
        LinkButton2.NavigateUrl = "FrameBottom.aspx?id=2";
        LinkButton2.Target = "fBottom";
        LinkButton3.NavigateUrl = "FrameBottom.aspx?id=3";
        LinkButton3.Target = "fBottom";
        
    }

In FrameBottom.aspx.cs

protected void Page_Load(object sender, EventArgs e)
    {
        string id=Request.QueryString["id"] ;
        OpenExcel(id);
    
    }

    private void OpenExcel(string id)
    {


        if (id == "1")
        {
            //use your own localhost : port no

            Response.Redirect(@"http://localhost:23265/TestProject/TempFiles/Excel 1.xls", true);


        
        }
        else if (id == "2")
        {
            Response.Redirect(@"http://localhost:23265/TestProject/TempFiles/fiber.bmp", true);
            


        }
        else
        {


            Response.Redirect(@"http://localhost:23265/TestProject/TempFiles/Excel 2.xls", false);

        }
        

    }

Create a folder also call TempFiles which contain excel documents(with multiple worksheet).

Thanks,
Bye.