I am building an ASP.NET 3.5 application in which I have a page which loads another page in a different domain in an iframe. Below is the for Default.aspx page:
<asp:Content ID="Content1" ContentPlaceHolderID="mainContent" runat="server">
    <iframe src="isite.aspx" runat="server" width="100%" height="100%" scrolling="auto">
    </iframe>
</asp:Content>
Below is the iframe page isite.aspx:
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head id="Head1" runat="server">
        <title>Untitled Page</title>
    </head>
    <body style="margin: 0; text-align: center;">
        <form id="Form1" name="frmSubmit" action="https://mysite.com/Login.asp"
        method="POST" runat="server">
        <span style="font-family: Arial">
            <asp:ImageButton ID="ImageButton1" runat="server" PostBackUrl="https://mysite.com/Login.asp" ImageUrl="/ajax-loader.gif" /> Please wait...
    <br />
        </span>
        <input type="hidden" name="txtUserName" size="30" maxlength="50" value="admin"
            onkeypress="Javascript:CheckKeyPress('ID')"/>
        <input type="hidden" name="pwdPassword" size="30" maxlength="25" value="password"
            onkeypress="Javascript:CheckKeyPress('P')"/>
        </form>
    </body>
    </html>
Below is the isite.aspx.cs page:
    protected void Page_Load(object sender, EventArgs e)
    {
        Page.ClientScript.RegisterStartupScript(Page.GetType(), "click", "<script language=javascript>document.getElementById('" + ImageButton1.ClientID + "').click();</script>");
    }
This works fine in Firefox,Safari and Chrome but it dosent work in IE 7 or 8. In IE it gives me a HTTP 500 error page. After doing some research on it I figured that its a cookie issue in IE and tried the below soutions:
- Added the following code to the Global.asax: - protected void Application_BeginRequest(object sender, EventArgs e) { HttpContext.Current.Response.AddHeader("p3p", "CP=\"IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT\""); } 
- Added the following line of code to the Page_Init and Page_Load events 
HttpContext.Current.Response.AddHeader("p3p", "CP=\"IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT\"");
None of these solutions worked for me. What am I missing?