Error is something like that :

Can't load Items.aspx from 192.168.0.172

And a text is Can't open this web-site. It can't be found. Try later

code :

   HttpContext.Current.Response.Clear();
    HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
    HttpContext.Current.Response.Charset = System.Text.Encoding.Unicode.EncodingName;
    HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.Unicode;
    HttpContext.Current.Response.BinaryWrite(System.Text.Encoding.Unicode.GetPreamble());
    HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";
    HttpContext.Current.Response.AddHeader(
         "content-disposition", string.Format(
            "attachment; filename={0}",fileName));

....

        table.RenderControl(htw);
        HttpContext.Current.Response.Write(sw.ToString());
        HttpContext.Current.Response.End();

Trouble with this file is only for Internet Explorer (works on opera / firefox ... )

And so it works for HTML with no

HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";

this string